JP2008173617A - Water treatment apparatus and water treating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment apparatus and a water treating method, capable of enhancing decomposition efficiency of organic compounds in water to be treated, and omitting arrangement of an oxidant removing device in the latter stage of an ultraviolet ray irradiation device. <P>SOLUTION: The water treatment apparatus is provided with a nitrous oxide adding means for adding nitrous oxide into the treating object water, the ultraviolet ray irradiation device irradiating the water to be treated in which nitrous oxide is added, with ultraviolet ray, for decomposing organic compounds in the water, and an ion exchange resin apparatus for removing ions in the water by introducing thereto the water treated in the ultraviolet ray irradiation device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water treatment apparatus and a water treatment method for removing organic compounds in water, and more particularly, to a water treatment apparatus and a water treatment method suitable for ultrapure water production.

  Conventionally, primary pure water that has been subjected to ion exchange treatment or reverse osmosis membrane treatment is irradiated with ultraviolet rays by an ultraviolet irradiation device to decompose organic compounds, and mixed bed type ion exchange resin devices and ultrafiltration membrane devices are used. 2. Description of the Related Art Ultrapure water production apparatuses that perform finishing treatment are known.

In order to decompose the organic compound efficiently, an ultrapure water production apparatus that irradiates ultraviolet rays in a state where hydrogen peroxide is dissolved in water to be treated is known. Moreover, in order to decompose | disassemble an organic compound efficiently, the ultrapure water manufacturing apparatus which adds ozone to to-be-processed water and irradiates with an ultraviolet-ray is proposed (for example, patent document 1).
JP-A-7-241598

However, ozone and hydrogen peroxide remaining in the water to be treated at the exit of the ultraviolet irradiation device cause oxidative degradation of the ion exchange resin constituting the ion exchange resin device and the membrane material constituting the ultrafiltration membrane. For this reason, there are problems such as deterioration components mixed into the water to be treated and water quality being lowered, and frequent exchange of ion exchange resins.
For this reason, when decomposing organic compounds in the treated water by irradiating ultraviolet rays with an ultraviolet irradiating device, ultraviolet radiation is used when ozone or hydrogen peroxide is added to the treated water to improve the decomposition efficiency of the organic compounds. It was necessary to provide an oxidant removing device for removing ozone and hydrogen peroxide at the subsequent stage of the apparatus and the preceding stage of the ion exchange resin apparatus. Examples of the oxidant removing device include a means for irradiating ultraviolet rays, but the means for irradiating ultraviolet rays is bulky, so that there are many cases where it is difficult to install it because of securing an empty space. Moreover, activated carbon can be cited as an oxidant removing device, but there are problems such as insufficient decomposition of hydrogen peroxide, short service life, and elution of pulverized coal. Therefore, there has been a demand for a water treatment technique that can improve the decomposition efficiency of the organic compound in the water to be treated and can omit the arrangement of the oxidant removing device.

  In view of the above, the present invention provides a water treatment device and a water treatment method that can improve the decomposition efficiency of organic compounds in the water to be treated and can omit the disposition of the oxidant removing device after the ultraviolet irradiation device. For the purpose.

  In order to achieve the above object, a water treatment apparatus according to the present invention irradiates ultraviolet light to water to be treated to which nitrous oxide is added, nitrous oxide addition means for adding nitrous oxide to the water to be treated, An ultraviolet irradiation device that decomposes an organic compound in water, and an ion exchange resin device that introduces water to be treated treated by the ultraviolet irradiation device and removes ions in water.

  ADVANTAGE OF THE INVENTION According to this invention, while improving the decomposition | disassembly efficiency of the organic compound in to-be-processed water, it can provide the water treatment apparatus and water treatment method which can abbreviate | omit to arrange | position an oxidizing agent removal apparatus in the back | latter stage of an ultraviolet irradiation device.

  Embodiments of the present invention will be specifically described below with reference to the drawings.

The present invention relates to a water treatment apparatus and a water treatment method, and will be described using an example of an ultrapure water production apparatus and an ultrapure water production method.
FIG. 1 is a diagram showing an example of the configuration of an ultrapure water production apparatus 1 according to the present invention. As shown in FIG. 1, the ultrapure water production apparatus 1 includes a pretreatment device 2, a two-bed / three-column ion exchange device 3, a reverse osmosis device 4, a deaeration device 5, and a nitrous oxide addition means 6. And an ultraviolet irradiation device 7, an ion exchange resin device 8, and an ultrafiltration membrane device 9. The ultrapure water production apparatus 1 is provided with a nitrous oxide removing means (not shown) downstream of the ultraviolet irradiation device 7 (for example, between the ultraviolet irradiation device 7 and the ion exchange resin device 8) as necessary. You can also.

  The raw water is introduced into the pretreatment device 2, and suspended substances and the like in the raw water are separated and removed. Next, the water to be treated treated by the pretreatment device 2 is reverse osmosis after the ionic components are removed by the two-bed / three-column ion exchange device 3 comprising a cation exchange resin tower, a decarboxylation tower and an anion exchange resin tower. The fine particles and colloidal substances are removed by being introduced into the apparatus 4. Next, the water to be treated is introduced into a degassing device 5 such as a nitrogen gas addition type vacuum degassing device to remove dissolved gases such as dissolved oxygen.

  Subsequently, after nitrous oxide is added to the water to be treated by the nitrous oxide addition means 6, the organic compound in the water to be treated is decomposed by being introduced into the ultraviolet irradiation device 7, for example, as in a mixed bed ion exchange device. The ion component in the water to be treated is removed by the ion exchange resin device 8. Finally, the water to be treated is introduced into the ultrafiltration membrane device 9 to remove a very small amount of fine particles and the like.

  Here, the pretreatment device 2 is the pretreatment system, the two-bed three-column ion exchange device 3 to the deaeration device 5 are the primary pure water system, and the nitrous oxide addition means 6 to the ultrafiltration membrane device 9 are the two. Separated from the next pure water system.

  Nitrous oxide addition means 6, ultraviolet irradiation device 7, ion exchange resin device 8, ultrafiltration membrane device 9, and ultrafiltration membrane device 9 provided in the ultrapure water production apparatus 1 in the secondary pure water system, are arranged as necessary. The nitrous oxide removing means will be described in detail below.

The nitrous oxide addition means 6 adds nitrous oxide (N ₂ O) gas to the water to be treated before the ultraviolet irradiation device 7 or the water to be treated in the ultraviolet irradiation device 7. As the nitrous oxide addition means 6, for example, there can be mentioned one by supply from a gas cylinder filled with nitrous oxide gas.
When nitrous oxide is added to the water to be treated by the nitrous oxide addition means 6, the decomposition efficiency of the organic compound in the water to be treated can be improved by irradiating the ultraviolet rays with the ultraviolet irradiation device 7.
Further, if nitrous oxide is used instead of ozone or hydrogen peroxide which has been conventionally used for improving the decomposition efficiency of organic compounds, it is conventionally arranged in the subsequent stage of the ultraviolet irradiation device 7 and the previous stage of the ion exchange resin device 8. The oxidant removing device that has been used can be omitted.

Further, if nitrous oxide is used instead of ozone or hydrogen peroxide which has been conventionally used for improving the decomposition efficiency of organic compounds, the ultraviolet irradiation device 7 outlet, the ion exchange resin device 8 outlet and the ultrafiltration membrane are used. An increase in the dissolved oxygen concentration of the water to be treated at the outlet of the apparatus 9 can be reduced.
Moreover, by adding nitrous oxide and irradiating ultraviolet rays with the ultraviolet irradiation device 7, it is difficult to remove such as urea in raw water (treated water), which has been difficult to remove with a conventional normal ultrapure water production device. Organic nitrogen can be decomposed efficiently.
In addition, improvement of decomposition efficiency of organic compounds by nitrous oxide, omission of arrangement of oxidant removing device, reduction of increase in dissolved oxygen concentration of treated water at outlet of ultraviolet irradiation device 7, etc., urea in treated water, etc. Details of the removal of organic nitrogen will be described later.

The ultraviolet irradiation device 7 irradiates the water to be treated with ultraviolet rays to decompose organic compounds in the water to be treated. A light source for irradiating ultraviolet rays having a wavelength of 240 nm or less capable of dissociating nitrous oxide (described later). I have. Examples of the light source of the ultraviolet irradiation device 7 include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, and an excimer lamp.
A light source such as a low-pressure mercury lamp may be disposed in the water to be treated, or may be disposed outside the water to be treated through a space. When the light source is disposed outside the water to be treated, it is preferable to fill the space between the light source and the water to be treated with an inert gas. This is because ultraviolet rays emitted from the light source can be absorbed by oxygen molecules in the atmosphere before being irradiated onto the water to be treated, thereby reducing the irradiation amount and generating ozone.

Since nitrous oxide is an inert gas, it does not function as an oxidizing substance even when it remains in the water to be treated, and the influence of pH change in the water to be treated can be ignored. Therefore, it is not always necessary to provide the ultrapure water production apparatus 1 with nitrous oxide removing means. However, if necessary, a nitrous oxide removing means (not shown) may be provided downstream of the ultraviolet irradiation device 7 (for example, between the ultraviolet irradiation device 7 and the ion exchange resin device 8).
The nitrous oxide removing means is for decomposing nitrous oxide remaining in the water to be treated after the ultraviolet irradiation device 7. Examples of the nitrous oxide removing means include an apparatus that irradiates the water to be treated with nitrous oxide remaining with ultraviolet light having a wavelength of 240 nm or less, a vacuum degassing apparatus, and the like.

The ion exchange resin device 8 is a device that removes ion components in the water to be treated including organic acids and the like decomposed and generated in the ultraviolet irradiation device 7, and for example, an anion exchange resin device filled with an anion exchange resin, or anion exchange A mixed type apparatus of resin and cation exchange resin can be mentioned.
The ultrafiltration membrane device 9 is a device that removes fine particles remaining in the water to be treated that has been treated in the ion exchange resin device 8, and is, for example, PAN (polyacrylonitrile), cellulose acetate, or fluorine-based one. A general ultrafiltration membrane device equipped with various ultrafiltration membranes can be used as appropriate.

By the nitrous oxide addition means 6, nitrous oxide is added to the water to be treated (primary pure water) containing the organic compound. The concentration of nitrous oxide (N ₂ O) dissolved in the water to be treated is preferably 5 mg / L or more and 1000 mg / L or less, more preferably 10 mg / L or more and 100 mg / L or less. If the concentration of nitrous oxide is less than 5 mg / L, the decomposition efficiency of the organic compound by adding nitrous oxide may not be sufficiently improved. Although the decomposition efficiency of organic compounds increases as the nitrous oxide concentration increases, if the nitrous oxide concentration exceeds 1000 mg / L, the nitrous oxide may be dissipated into the atmosphere and the cost may increase. There is a risk of bubbles being generated.

When ultraviolet light containing a wavelength of 240 nm or less is irradiated to the water to be treated to which nitrous oxide has been added by the ultraviolet irradiation device 7, the nitrous oxide reacts as shown in the reaction formula (1), and enters the water to be treated. Excited oxygen atoms (O) are generated.
N ₂ O → N ₂ + O (1)
The excited oxygen atom (O) immediately reacts with water as shown in the reaction formula (2) to generate a hydroxy radical (.OH).
O + H ₂ O → 2.OH (2)
When nitrous oxide is added to the water to be treated and irradiated with ultraviolet rays, hydroxy radicals are generated from nitrous oxide in this way, so the generation of hydroxy radicals in water is accelerated, and ultraviolet rays are added without adding nitrous oxide. Compared with the case of irradiation, the decomposition efficiency of the organic compound can be improved.

In addition, hydroxy radicals are also generated by the following reaction formulas (3) and (4).
When the water to be treated is irradiated with ultraviolet rays, the water is decomposed by the reaction formula (3) to generate hydroxy radicals (.OH) and hydrogen radicals (.H).
H ₂ O → OH + H (3)
Heretofore, it has been known that this .H reacts with an organic radical, which is an intermediate product in the .OH decomposition process of an organic compound, to hinder the decomposition process of the organic compound. In this embodiment, since nitrous oxide is added to the water to be treated, nitrous oxide that has not been decomposed by ultraviolet rays can react with .H as represented by the reaction formula (4).
N ₂ O + · H → N ₂ + · OH (4)
As a result, the reaction between .H and an organic radical can be suppressed, a hydroxy radical can be generated, and the decomposition efficiency of the organic compound can be improved.

  The hydroxy radicals generated by the reaction formulas (1) to (4) oxidize and decompose organic compounds in the water to be treated. The organic compounds are oxidatively decomposed into organic acids such as carboxylic acids, and some of them are decomposed into carbon dioxide. The

When the organic compound in the water to be treated is decomposed by irradiating the ultraviolet ray with the ultraviolet irradiation device 7, nitrous oxide is used instead of ozone and hydrogen peroxide which are conventionally used to improve the decomposition efficiency of the organic compound. It is added to the treated water.
Conventionally used ozone generates O ₂ by the irradiation of ultraviolet rays by the ultraviolet irradiation device 7 and increases the dissolved oxygen concentration in the water to be treated at the outlet of the ultraviolet irradiation device 7. Further, hydrogen peroxide that has been conventionally used is decomposed into oxygen and water in the vicinity of the surface of the ion exchange resin filled in the ion exchange resin device 8, and the dissolved oxygen concentration in the treated water that has passed through the ion exchange resin device 8 is reduced. increase. Moreover, oxygen is also generated when ozone or hydrogen peroxide remaining in the subsequent stage of the ultraviolet irradiation device 7 is decomposed using an oxidant removing device described later, and dissolved oxygen in the water to be treated is increased.
In contrast, nitrous oxide used in the present invention does not generate O ₂ by irradiation with ultraviolet rays, as shown in reaction formulas (1) and (2). Moreover, since nitrous oxide is a stable substance, its reactivity with the ion exchange resin filled in the ion exchange resin device 8 is low, and there is almost no generation of O ₂ due to decomposition in the vicinity of the ion exchange resin. Therefore, in the ultrapure water production apparatus 1 of the present invention, it is possible to reduce the increase in the dissolved oxygen concentration of the water to be treated at the outlet of the ultraviolet irradiation device 7, the outlet of the ion exchange resin device 8, and the outlet of the ultrafiltration membrane device 9. it can.

The ultraviolet rays irradiated to the water to be treated containing nitrous oxide preferably have a wavelength in the range of 173 nm to 240 nm. When the wavelength of ultraviolet rays exceeds 240 nm, nitrous oxide does not absorb light exceeding 240 nm, so that nitrous oxide (N ₂ O) does not dissociate into N ₂ and O, which can improve the decomposition efficiency of organic compounds. Have difficulty. Further, when the wavelength of ultraviolet rays is less than 173 nm, the absorption peak of ultraviolet rays by water is 167 nm, and the absorption peak of ultraviolet rays of nitrous oxide is 190 nm, so that the proportion of absorption of ultraviolet rays by water increases. As a result, the power cost may increase.

  The temperature of the water to be treated containing nitrous oxide is preferably 15 ° C. or higher and 30 ° C. or lower. If the temperature of the water to be treated is less than 15 ° C, the decomposition rate of the organic compound may be reduced. If the temperature of the water to be treated exceeds 30 ° C, the concentration of nitrous oxide dissolved in the water to be treated is reduced. There is a risk of it.

  If necessary, a nitrous oxide removing means (not shown) may be provided downstream of the ultraviolet irradiation device 7 to remove nitrous oxide remaining in the water to be treated treated by the ultraviolet irradiation device 7.

  Ionic components in the water to be treated such as organic acid and carbon dioxide decomposed and generated in the ultraviolet irradiation device 7 are removed by the ion exchange resin device 8, and finally, an extremely small amount of fine particles and the like are removed by the ultrafiltration membrane device 9. Ultrapure water (secondary pure water) having a low total organic carbon concentration (TOC) can be obtained.

When the organic compound in the water to be treated is decomposed by irradiating the ultraviolet ray with the ultraviolet irradiation device 7, nitrous oxide is used instead of ozone and hydrogen peroxide which are conventionally used to improve the decomposition efficiency of the organic compound. It is added to the treated water.
If ozone or hydrogen peroxide used in the past remains in the water to be treated at the exit of the ultraviolet irradiation device 7, the ion exchange resin constituting the ion exchange resin device 8, the hollow fiber of the ultrafiltration membrane device 9, etc. There have been problems such as oxidative deterioration, deterioration components mixed into the water to be treated and water quality being lowered, and frequent exchange of ion exchange resins. For this reason, conventionally, it has been necessary to provide an oxidizing agent removing device (for example, means for irradiating ultraviolet rays or activated carbon) to remove ozone and hydrogen peroxide after the ultraviolet irradiation device and before the ion exchange resin device. It was.
On the other hand, since nitrous oxide used in the present invention does not function as an oxidizing agent because of the inert gas, even if nitrous oxide remains in the water to be treated at the outlet of the ultraviolet irradiation device 7, The ion exchange resin constituting the exchange resin device 8 and the hollow fiber of the ultrafiltration membrane device 9 are not oxidatively deteriorated. Therefore, in the ultrapure water production apparatus 1 of the present invention, the oxidant removing apparatus that has been conventionally arranged in the subsequent stage of the ultraviolet irradiation apparatus 7 and the previous stage of the ion exchange resin apparatus 8 can be omitted.

Since the ultrapure water production apparatus 1 of the present invention includes the nitrous oxide addition means 6, urea in raw water (treated water) that has been difficult to remove by a conventional normal ultrapure water production apparatus. It is possible to decompose and remove organic nitrogen such as.
In raw water (river water, groundwater, etc.) for producing ultrapure water, urea (NH ₂ CONH ₂ ) is contained, for example, derived from nitrogen fertilizer, pharmaceutical raw materials, and the like. However, it is not easy to remove urea with a conventional normal ultrapure water production apparatus. The removal rate of urea in the reverse osmosis device is, for example, about 60%, it is difficult to decompose urea in the ultraviolet irradiation device, and urea is not exchanged in the ion exchange resin device. For this reason, urea accounts for 50% or more of all organic carbon (TOC) in ultrapure water, and urea in raw water has been a cause of hindering the reduction of TOC in ultrapure water.
On the other hand, the ultrapure water production apparatus 1 of the present invention decomposes urea by irradiating ultraviolet rays with the ultraviolet irradiation device 7 in a state where nitrous oxide is added by the nitrous oxide addition means 6, and the ion exchange resin device 8. By removing the decomposition component of urea, the urea in the water to be treated can be efficiently decomposed and removed.

  Thus, by using the ultrapure water production apparatus 1 provided with the nitrous oxide addition means 6, the total organic carbon (TOC) concentration in the for-treatment water is set to 0.5 mg in the raw water (the for-treatment water), for example. / L to, for example, 1 μg / L.

  As described above, when the ultrapure water production apparatus 1 of the present invention decomposes an organic compound in water to be treated by irradiating ultraviolet rays with the ultraviolet ray irradiating device 7, it adds nitrous oxide to the water to be treated. The decomposition efficiency of the organic compound in the for-treatment water can be improved.

  In addition, when the organic compound in the water to be treated is decomposed by irradiating the ultraviolet ray with the ultraviolet irradiation device 7, nitrous oxide is used in place of ozone or hydrogen peroxide conventionally used for improving the decomposition efficiency of the organic compound. Is added to the water to be treated. Since nitrous oxide does not function as an oxidizing agent because of inert gas, even if nitrous oxide remains in the water to be treated at the outlet of the ultraviolet irradiation device 7, the ion exchange resin that constitutes the ion exchange resin device 8 Etc. are not deteriorated by oxidation. On the other hand, when ozone or hydrogen peroxide that has been conventionally used is added, if ozone or hydrogen peroxide remains in the water to be treated at the outlet of the ultraviolet irradiation device 7, ozone or hydrogen peroxide is oxidized. As a result, the ion exchange resin or the like constituting the ion exchange resin device 8 is oxidized and deteriorated. Therefore, in the ultrapure water production apparatus 1 of the present invention, since nitrous oxide that does not function as an oxidant is added, oxidative deterioration of the ion exchange resin or the like can be prevented, the latter stage of the ultraviolet irradiation apparatus 7 and the ion exchange resin. Arranging an oxidant removing device (for example, a means for irradiating ultraviolet rays or activated carbon) in front of the device 8 can be omitted. Thus, the water treatment apparatus and the water treatment method of the present invention can simplify the configuration of the water treatment apparatus and the manufacturing process.

  In addition, if nitrous oxide that does not function as an oxidant is added instead of ozone or hydrogen peroxide that has been used in the past, oxidative deterioration of the ion exchange resin or the like charged in the ion exchange resin device 8 can be prevented. It can reduce that deterioration components, such as exchange resin, mix in ultrapure water. For this reason, the water treatment apparatus and water treatment method of the present invention can obtain ultrapure water with stable quality, and are suitable for the production of ultrapure water.

Moreover, since the ultrapure water production apparatus 1 of the present invention can reduce the increase in the dissolved oxygen concentration of the water to be treated at the outlet of the ultraviolet irradiation device 7, the outlet of the ion exchange resin device 8, and the outlet of the ultrafiltration membrane device 9, In order to remove dissolved oxygen, it is not necessary to provide a dissolved oxygen removing means such as a deaeration device in the subsequent stage of the ultraviolet irradiation device (for example, between the ultraviolet irradiation device 7 and the ion exchange resin device 8). Therefore, the water treatment apparatus and the water treatment method of the present invention can simplify the configuration of the water treatment apparatus and the manufacturing process.
Further, according to the ultrapure water production apparatus 1 of the present invention, the increase in dissolved oxygen concentration of the water to be treated at the outlet of the ultraviolet irradiation apparatus 7 can be reduced, so that the latter stage of the ultraviolet irradiation apparatus (for example, ion exchange with the ultraviolet irradiation apparatus 7). Even when a dissolved oxygen removing means such as a deaerator is provided between the resin devices 8), the load of the dissolved oxygen removing means can be reduced.
The dissolved oxygen concentration in ultrapure water is required to be 3 μg / L or less in semiconductor cleaning with a large amount of ultrapure water used (International Semiconductor Technology Roadmap, ITRS: International Technology Roadmap for Semiconductors). The water treatment apparatus and the water treatment method of the present invention reduce the load of the dissolved oxygen removing means even when the arrangement of the dissolved oxygen removing means in the subsequent stage of the ultraviolet irradiation device 7 is omitted or when the dissolved oxygen removing means is provided. Therefore, it is suitable for the production of ultrapure water.

Moreover, according to the ultrapure water production apparatus 1 of the present invention, organic nitrogen such as urea in raw water (treated water), which has been difficult to remove by a conventional normal ultrapure water production apparatus, is efficiently used. Can be decomposed and removed. That is, in a state in which nitrous oxide is added by the nitrous oxide addition means 6, ultraviolet rays are irradiated by the ultraviolet irradiation device 7 to decompose urea, and urea decomposition components are removed by the ion exchange resin device 8, and the treated water is removed. The urea can be efficiently decomposed and removed. Thereby, in the ultrapure water manufacturing apparatus 1 of this invention, TOC in ultrapure water can be reduced rather than before.
Moreover, according to the ultrapure water production apparatus 1 of the present invention, it is possible to stably produce ultrapure water below the TOC target value. The concentration of urea in the raw water varies depending on various factors such as region and season. In the conventional normal ultrapure water production apparatus, since it was difficult to remove urea, the TOC in the obtained ultrapure water increases as the urea concentration in the raw water increases. According to the ultrapure water production apparatus 1 of the present invention, even when the concentration of urea in the raw water is high, urea can be decomposed and removed to reduce the TOC in the ultrapure water. Can be manufactured stably.

In addition, embodiment of this invention is not restricted to said embodiment, It can expand and change, Embodiment which expanded and changed is also contained in the technical scope of this invention.
For example, the ultraviolet irradiation device and the ion exchange resin device arranged at the subsequent stage of the ultraviolet irradiation device may be provided in, for example, the primary pure water system, or may be provided in both the primary pure water system and the secondary pure water system. Good.
In the above-described embodiment, the ultrapure water production apparatus 1 has been described as an example of the water treatment apparatus including the nitrous oxide addition means 6, the ultraviolet irradiation apparatus 7, and the ion exchange resin apparatus 8. The apparatus is not limited to the ultrapure water production apparatus, and may be configured as, for example, a pure water production apparatus, a waste water treatment apparatus, a water purification treatment apparatus, or the like.

  Hereinafter, the content of the present invention will be described using examples, but the present invention is not limited to these examples.

(Example 1)
FIG. 2 is a diagram illustrating a configuration of a simulated organic compound decomposition apparatus 10 including a nitrous oxide addition unit and an ultraviolet irradiation device. The organic compound simulated decomposition apparatus 10 includes a glass container 11 storing a urea aqueous solution as a simulated aqueous solution, a stirrer 12 for stirring the urea aqueous solution, and an ultraviolet ray disposed in the urea aqueous solution and having a wavelength of 240 nm or less. UV irradiation device 13 (comprised of quartz test tube 14 and low-pressure ultraviolet lamp 15 disposed in quartz test tube 14), and nitrous oxide addition for adding nitrous oxide gas to aqueous urea solution Means 16 (comprised of an N ₂ O gas supply line 17 and a glass diffuser pipe 18 connected to the N ₂ O gas supply line 17 for bubbling nitrous oxide gas into the urea aqueous solution).

An aqueous urea solution is accommodated in the container 11, nitrous oxide gas is supplied from the N ₂ O gas supply line 17, added while being bubbled into the aqueous urea solution through the glass diffuser 18, and irradiated with ultraviolet rays by the ultraviolet irradiation device 13. The organic compound decomposition test using the organic compound decomposition simulation apparatus 10 was performed. The test conditions are initial urea concentration 1 mg · C / L, urea aqueous solution amount 3 L, temperature 23 ° C., UV output 1.32 W, N ₂ O gas purity 99.999 vol% or more, injection N ₂ O gas flow rate 5 mL / min. .
The total organic carbon concentration (TOC) in the urea aqueous solution was measured, and the change in the TOC residual rate (100 × residual organic carbon concentration / initial organic carbon concentration) with respect to the amount of ultraviolet irradiation was determined. FIG. 3 is a diagram showing a result of decomposing urea using the simulated decomposition apparatus 10 for organic compounds. In FIG. 3, as a comparative example, the case of irradiating ultraviolet rays is also shown in exactly the same manner as in Example 1 except that nitrous oxide was not added. The vertical axis of FIG. 3 indicates the TOC residual rate (100 × residual organic carbon concentration / initial organic carbon concentration) (%), and the horizontal axis indicates the amount of ultraviolet irradiation (kW · hr / m ³ ).

As apparent from FIG. 3, when the urea aqueous solution was irradiated with ultraviolet rays of 4 kW · hr / m ³ without adding nitrous oxide (comparative example), the decrease in the TOC concentration was about 4%. On the other hand, when nitrous oxide was added and irradiated with ultraviolet rays of 4 kW · hr / m ³ , the decrease in TOC concentration exceeded 20%.
Therefore, it was confirmed that by adding nitrous oxide to the water to be treated, the decomposition efficiency of the organic compound by ultraviolet irradiation was improved.
In addition, by adding nitrous oxide to the water to be treated and irradiating it with ultraviolet rays, it is possible to efficiently decompose urea in the water to be treated, which was difficult to remove with conventional conventional ultrapure water production equipment. Was confirmed.

(Example 2)
Using the ultrapure water production apparatus 1 of FIG. 1, ultrapure water was produced continuously over time. Tap water was used as raw water supplied to the pretreatment device 2. The degassing device 5 is a nitrogen gas addition type vacuum degassing device in which the volume ratio of nitrogen gas to water to be treated is 0.03: 1. The nitrous oxide addition means 6 is based on supply from a gas cylinder filled with nitrous oxide gas, and the concentration of nitrous oxide in the water to be treated immediately after the addition of nitrous oxide is 20 mg / L. The ultraviolet irradiation device 7 is a low-pressure ultraviolet lamp (Chiyoda Chemical Co., Ltd., low-pressure UV oxidation lamp, irradiation amount 0.25 kWh / m ³ ), and generates ultraviolet light having a peak at a wavelength around 185 nm. The temperature was 23 ° C.

  For comparison, the ultrapure water was treated in the same manner as in Example 2 except that ozone gas or hydrogen peroxide was added without adding nitrous oxide in the previous stage of the ultraviolet irradiation device 7. Manufactured continuously. The ozone concentration in the treated water immediately after the addition of ozone is 7.3 mg / L, and the hydrogen peroxide concentration in the treated water immediately after the addition of hydrogen peroxide is 7 mg / L.

  For each case where nitrous oxide, ozone (comparative example), or hydrogen peroxide (comparative example) was added to the dissolved oxygen concentration in the water to be treated at the outlet of the ultrafiltration membrane device 9, a diaphragm type dissolved oxygen meter Was measured respectively.

When nitrous oxide was added, the dissolved oxygen concentration in the water to be treated at the outlet of the ultrafiltration membrane device 9 was 1.0 mg / L or less, whereas when ozone was added (comparative example) Was 8.2 mg / L, and 7.1 mg / L when hydrogen peroxide was added (Comparative Example).
Therefore, when the organic compound in the water to be treated is decomposed by irradiating the ultraviolet ray with the ultraviolet irradiation device 7, nitrous oxide is used in place of ozone or hydrogen peroxide conventionally used for improving the decomposition efficiency of the organic compound. It was confirmed that the increase in the dissolved oxygen concentration of the water to be treated at the outlet of the ultrafiltration membrane device 9 can be reduced by adding to the water to be treated.
Further, when nitrous oxide was added, no deterioration or decomposition of the ion exchange resin filled in the ion exchange resin device 8 or the hollow fibers constituting the ultrafiltration membrane device 9 was confirmed.
In addition, when nitrous oxide was added, the TOC of the obtained ultrapure water was 1 μg / L or less, and it was confirmed that high quality ultrapure water was obtained by the ultrapure water production apparatus 1.

(Example 3)
After the urea in the urea aqueous solution, which is a simulated aqueous solution, is decomposed by the simulated organic compound decomposition apparatus 10 in FIG. 2, the simulated aqueous solution after the decomposition treatment is passed through an anion exchange resin to perform a decomposition removal test of urea. It was.
The test conditions in the simulated decomposition apparatus 10 are: initial urea concentration 1 mg · C / L, urea aqueous solution amount 3 L, temperature 23 ° C., UV output 1.32 W, N ₂ O gas purity 99.999 vol% or more, injected N ₂ O gas It was carried out under two conditions (1.1 kW · hr / m ³ , 2.3 kW · hr / m ³ ) with a flow rate of 5 mL / min and different ultraviolet irradiation amounts. The nitrous oxide concentration in the urea aqueous solution immediately after the addition of nitrous oxide was 98 mg / L.
100 mL of A101 (Rohm and Haas Japan) was used as the anion exchange resin, and the liquid flow rate through the anion exchange resin was 10 mL / min.

Urea is decomposed by the organic compound simulated decomposition apparatus 10 and the TOC (U1) of the simulated aqueous solution before passing through the anion exchange resin and the TOC (U2) of the simulated aqueous solution after passing through the anion exchange resin are measured. The urea-derived TOC removal concentration (U1-U2) was determined. FIG. 4 is a diagram showing a result of decomposing and removing urea in an aqueous urea solution using the simulated organic compound decomposition apparatus 10 and an anion exchange resin. FIG. 4 shows a case where urea is decomposed and removed in the same manner as in Example 3 except that nitrous oxide is not added in the simulated organic compound decomposition apparatus 10 as a comparative example. The vertical axis in FIG. 4 represents the urea-derived TOC removal concentration (μg / L), and the horizontal axis represents the ultraviolet irradiation amount (kW · hr / m ³ ).

As is clear from FIG. 4, when nitrous oxide is added to an aqueous urea solution and irradiated with ultraviolet light, the TOC derived from urea is compared with the case of irradiating ultraviolet light without adding nitrous oxide to the aqueous urea solution. The removal concentration increased about 3-5 times.
Therefore, it was confirmed that urea in the water to be treated can be efficiently decomposed and removed by adding nitrous oxide to the water to be treated and irradiating it with ultraviolet rays and then passing it through an ion exchange resin apparatus.

It is a figure which shows an example of a structure of the ultrapure water manufacturing apparatus of this invention. It is a figure which shows the structure of the simulated decomposition apparatus of the organic compound provided with the nitrous oxide addition means and the ultraviolet irradiation device. It is a figure which shows the result of having decomposed | disassembled urea using the simulation decomposition apparatus of the organic compound. It is a figure which shows the result of decomposing | disassembling and removing urea in to-be-processed water using the simulated decomposition apparatus and anion exchange resin of an organic compound.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrapure water manufacturing apparatus, 2 ... Pretreatment apparatus, 3 ... Two bed 3 tower type ion exchange apparatus, 4 ... Reverse osmosis apparatus, 5 ... Deaeration apparatus, 6 ... Nitrous oxide addition means, 7 ... Ultraviolet irradiation apparatus , 8 ... ion exchange resin device, 9 ... ultrafiltration membrane device, 10 ... simulated decomposition device of organic compound, 11 ... container, 12 ... stirrer, 13 ... ultraviolet irradiation device, 14 ... quartz test tube, 15 ... low pressure ultraviolet light lamp, 16 ... nitrous oxide adding means, 17 ... _{N 2} O gas supply line, 18 ... glass diffuser tube.

Claims (10)

Nitrous oxide addition means for adding nitrous oxide to the water to be treated;
An ultraviolet irradiation device that irradiates the water to be treated with the nitrous oxide added with ultraviolet rays, and decomposes organic compounds in the water;
An ion exchange resin device for introducing treated water treated by the ultraviolet irradiation device and removing ions in the water;
A water treatment apparatus comprising:   The water treatment apparatus according to claim 1, wherein ultraviolet rays generated from the ultraviolet irradiation device have a wavelength within a wavelength range of 173 nm to 240 nm.   The water treatment apparatus according to claim 1 or 2, wherein the ion exchange resin apparatus is an anion exchange resin apparatus or a mixed type apparatus of an anion exchange resin and a cation exchange resin.   The water treatment apparatus according to any one of claims 1 to 3, wherein the organic compound contains urea.   The water treatment apparatus according to claim 1, wherein the water treatment apparatus is an ultrapure water production apparatus. Adding nitrous oxide to the water to be treated;
Irradiating ultraviolet rays to the water to be treated to which the nitrous oxide is added, and decomposing the organic compound;
Treating the water to be treated in which the organic compound is decomposed with an ion exchange resin device;
Water treatment method characterized by comprising.   The water treatment method according to claim 6, wherein the ultraviolet ray has a wavelength within a wavelength range of 173 nm to 240 nm.   The water treatment method according to claim 6 or 7, wherein the ion exchange resin device is an anion exchange resin device or a mixed type device of an anion exchange resin and a cation exchange resin.   The water treatment method according to any one of claims 6 to 8, wherein the organic compound contains urea.   The water treatment method according to any one of claims 6 to 9, wherein the water treatment method is an ultrapure water production method.

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