JPH10202296A - Ultrapure water producer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove org. matter in the lines (e.g. recovery line and secondary pure water line) for removing the org. matter in the water to be treated in an ultrapure water producer for cleaning the silicon wafer in the semiconductor industry. SOLUTION: This producer is provided with a reverse-osmosis membrane device 42 for passing the water to be treated contg. org. matter and an org. matter oxidizing device 44 for oxidizing and decomposing the org. matter in the water permeated through the device 42 by adding ozone to the water under alkaline conditions. In the org. matter oxidizing device 44, ozone is added to the water to be treated by a gas-liq. agitating and mixing means, ozone is added to the water kept at >=pH 9.7, and the ozone is preferably added by 3-40ppm. Besides, an anion-exchange device 40 using an OH-type anion-exchange resin can be provided instead of the reverse-osmosis device 42 on the upstream side of the membrane device 42 or between the device 42 and the org. matter oxidizing device 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing ultrapure water used for cleaning silicon wafers in the semiconductor industry, for example. The present invention relates to an ultrapure water production apparatus for improving the efficiency of removing organic substances in a recovery system or a secondary pure water system. Note that, in this specification, high-purity water, which is generally described in terms of pure water, ultrapure water, and the like, which are not necessarily clearly defined, is collectively referred to as “ultrapure water”.

[0002]

2. Description of the Related Art As shown in FIG. 7, an apparatus for producing ultrapure water used for cleaning a silicon wafer or the like generally includes a primary pure water system 2, a secondary pure water system (subsystem) 4, and a wastewater recovery system. A pure water drainage recovery system 6 is provided. The primary pure water system 2 is a path provided with, for example, a reverse osmosis membrane device, a vacuum deaerator, an ion exchange device, and the like, and a part of suspended substances and organic substances contained in raw water such as city water and industrial water is used. After being removed by a treatment system (not shown), the treated water 8 is supplied to the primary pure water system 2. The secondary pure water system 4 is a path provided with, for example, an ultraviolet oxidation device, a cartridge polisher, an ultrafiltration membrane device, and the like. It is supplied to the secondary pure water system 4. Part of the ultrapure water 12 obtained in the secondary pure water system 4 is sent to a use place 14 for use, and the remainder is circulated to a pure water storage tank 10. The pure water wastewater recovery system 6 is a path provided with, for example, an activated carbon filtration device, an ion exchange device, an ultraviolet oxidation device, and the like, and performs a treatment of the wastewater 16 generated by using ultrapure water at the use place 14. The treated water 18 of the pure water drainage recovery system 6 is returned to the primary pure water system 2 and reused.

[0003] In a general ultrapure water producing apparatus, as a wastewater recovery system for treating wastewater 16 generated by using ultrapure water discharged from the place of use 14, a primary treatment is performed after an appropriate treatment. The pure water drainage recovery system 6 for returning to the pure water system
In addition to the above, according to the cleanliness of the wastewater, a route to return directly to the primary pure water system without any treatment, a route to be used as miscellaneous water after performing appropriate treatment (miscellaneous wastewater collection system), and A route (wastewater treatment system) for discharging after appropriate treatment is provided.

[0004]

In the process of cleaning silicon wafers and the like in the semiconductor industry, organic cleaning agents such as isopropyl alcohol, methanol, and acetone are used. Usually, a trace amount of organic matter is contained, but the concentration of impurities in the wastewater from this place of use is extremely low as compared with city water, industrial water and the like. Therefore, if the organic matter concentration in the wastewater from the place of use is reduced as much as possible in the pure water wastewater recovery system of the ultrapure water production equipment and the treated water is returned to the primary pure water system, high purity ultrapure water can be obtained. It will be very advantageous. Therefore, in the wastewater recovery system for pure water, it is desired to remove organic substances as much as possible from the water to be treated.

[0005] In this case, as a method for removing organic substances in the pure water wastewater recovery system, conventionally, ozone or hydrogen peroxide as an oxidizing agent is added to the water to be treated (drainage), and further, ozone or hydrogen peroxide is contained. There is known a method in which water to be treated is irradiated with ultraviolet rays to oxidatively decompose organic substances.

However, this method has a drawback that the processing time is long because the decomposition rate of organic substances is low and the processing efficiency is low. Further, the use of a high-pressure ultraviolet lamp increases the size and complexity of the apparatus, increases the running cost, and is economically disadvantageous.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrapure water production apparatus which can efficiently remove organic substances in a path for removing organic substances from water to be treated.

[0008]

Means for Solving the Problems The present inventors have adjusted the pH of water to be treated containing organic substances to a specific range on the alkali side, and added ozone to the alkaline water to be treated. It was found that the organic matter in the water to be treated can be efficiently removed without performing the treatment. In this method, an organic substance is oxidatively decomposed by a hydroxy radical generated by a reaction between ozone and an alkali.

The present inventors have further studied the above-mentioned organic substance decomposition method. As a result, when ozone is added to the water to be treated under alkaline conditions to oxidize and decompose organic substances, the ionic water is contained in the water to be treated. Impurities, especially anionic impurities such as chloride ions and fluoride ions, inhibit the oxidative decomposition reaction of organic substances and reduce the efficiency of removing organic substances. On the other hand, the addition of ozone to the water to be treated If the water to be treated is treated with a reverse osmosis membrane device before performing the above, anionic impurities that inhibit the oxidative decomposition reaction of organic substances are removed from the water to be treated, and organic substances in the water to be treated are considerably removed. It has been found that the removal efficiency of organic substances at the time of adding ozone is improved.

[0010] The present invention has been made based on the above findings, and includes a reverse osmosis membrane device for passing water to be treated containing an organic substance, and adding ozone to the permeated water of the reverse osmosis membrane device under alkaline conditions. And an organic substance oxidizing apparatus for oxidizing and decomposing organic substances contained in the permeated water.

[0011] The ultrapure water apparatus of the present invention is used in a path for removing organic substances, particularly organic substances in the water to be treated containing a trace amount of organic substances, such as a wastewater recovery system for pure water and a secondary pure water system. A reverse osmosis membrane device and an organic matter oxidation device are installed. In this case, there is no restriction on the type of reverse osmosis membrane device,
A variety of reverse osmosis membrane devices can be used, for example, a reverse osmosis membrane device using a synthetic composite membrane such as a polyamide-based or aramid-based membrane, or a reverse osmosis membrane device using a cellulose-based membrane such as a cellulose acetate membrane is used. However, a reverse osmosis membrane device using a polyamide-based composite membrane is particularly preferred in that it has excellent organic matter removal performance. Further, the reverse osmosis membrane device may be of any type such as a spiral type, a hollow fiber type, a tubular type and the like.

Although there is no limitation on the structure of the organic oxidation apparatus, it is preferable that the apparatus satisfies one or more, particularly all of the following conditions. Ozone is added to the water to be treated by gas-liquid stirring and mixing means. Ozone is added to the water to be treated under alkaline conditions where the pH of the water to be treated is 9.7 or more. Ozone is added to the water to be treated so that the amount of ozone added to the water to be treated is 3 to 40 ppm.

That is, when ozone is added to the water to be treated, ozone has low solubility in water, so that it is not sufficiently dissolved in water by bubbling using a diffuser plate, and the oxidative decomposition reaction of organic substances is efficiently performed. Although it is difficult, ozone can be sufficiently dissolved in the water to be treated by using the gas-liquid stirring and mixing means, and the oxidative decomposition reaction of organic substances is efficiently performed. Therefore, it is preferable that the organic material oxidizing device has the following conditions.

In this case, the gas-liquid stirring and mixing means refers to a means for mixing a gas and a liquid while stirring them to dissolve the gas in the liquid. As a method for dissolving ozone using such a means, for example, water to be treated and ozone are introduced into the suction side of a pump equipped with a rotating blade, and the water to be treated and ozone are stirred and mixed by rotation of the rotating blade. Ozone is dissolved in the water to be treated by stirring and mixing, and the water to be treated in which the ozone is dissolved is sent to the treatment system through a pipe connected to the discharge side of the pump (ozone dissolving pump). Then, a pressurized water flow is supplied by an ejector or the like, and the water to be treated and ozone are stirred and mixed by the movement of the water flow to dissolve ozone in the water to be treated. Further, a line mixer having a stirring mechanism provided with a rotating blade inside a sealed container formed with a sealed blade in the middle of the pipe can also be used.

FIG. 6 shows that a plurality of waters (TOC concentration: 2000 ppb) containing an organic substance are prepared, each of which is adjusted to various different pHs by adding an alkali, and 9.6 ppm of ozone is added to oxidize the organic substance. This shows how the degree of decomposition changes depending on the initial pH value. TOC on the vertical axis of the graph indicates the residual TOC after 10 minutes from the ozone reaction. According to the figure, pH 9.7 or more,
Especially pH 9.7 to 11.0, especially pH 10.0 to 1
It can be seen that the decomposition rate of organic matter is high in the range of 0.5. Therefore, it is preferable that the organic material oxidizing device has the following conditions.

Further, if the amount of ozone added to the water to be treated is less than 3 ppm, the oxidative decomposition of organic substances becomes insufficient, and even if added in more than 40 ppm, the oxidative decomposition of organic substances is not further promoted, but also does not contribute to the reaction. Increases, which is not desirable in terms of processing cost. Therefore, it is preferable that the organic material oxidizing device has the following conditions. A more preferable range of the amount of ozone added to the water to be treated is 7 to 30 ppm.

In the organic matter oxidizing apparatus used in the present invention, the pH of the water to be treated may be adjusted before dissolving ozone in the water to be treated. The pH may be adjusted, and the pH adjustment of the water to be treated and the ozone dissolution in the water to be treated may be performed simultaneously. When the pH of the water to be treated is originally an appropriate value, the ozone may be dissolved in the water to be treated without adjusting the pH of the water to be treated. When ozone is added to the water to be treated under alkaline conditions, the oxidative decomposition reaction of the organic matter in the water to be treated starts immediately. However, by heating the water to be treated, the oxidative decomposition rate of the organic matter can be increased.

In the apparatus for producing ultrapure water according to the present invention, an anion exchange apparatus using an OH type anion exchange resin is provided upstream of the reverse osmosis membrane apparatus or between the reverse osmosis membrane apparatus and the organic matter oxidation apparatus. Can be provided. Thereby, anionic impurities that inhibit the oxidative decomposition reaction of the organic substance in the organic substance oxidizing apparatus can be more highly removed, and the removal efficiency of the organic substance in the organic substance oxidizing apparatus can be further increased. In addition, cations such as sodium ions are contained in the water to be treated, and when the water to be treated is passed through an anion exchange device, sodium hydroxide and the like are generated. Become. Therefore,
In the subsequent organic oxidation apparatus, it is not necessary to add an alkali agent for making the water to be treated alkaline, or it is possible to reduce the addition amount.

In this case, the type of the anion exchange resin in the anion exchange apparatus is not limited, and either a weakly basic anion exchange resin or a strongly basic anion exchange resin can be used. When the anion exchange device is installed in the wastewater recovery system for pure water in the wastewater recovery system, a weakly basic anion exchange resin is particularly preferable. The reason is that the water to be treated sent to the wastewater recovery system for pure water usually contains acids such as hydrofluoric acid, so that the water to be treated is usually acidic. This is because the resin can sufficiently remove anions such as fluoride ions, and the weakly basic anion exchange resin has a larger ion exchange capacity than the strongly basic anion exchange resin.

Further, since the anion exchange apparatus has the above-mentioned action, the apparatus for producing ultrapure water of the present invention is provided with an anion exchange apparatus using an OH type anion exchange resin instead of the reverse osmosis membrane apparatus. The water to be treated containing an organic substance may be treated by the anion exchange device, and the organic matter contained in the treated water of the anion exchange device may be oxidatively decomposed by an organic matter oxidation device. In the apparatus having this configuration, it is possible to remove anionic impurities from the water to be treated, thereby improving the efficiency of removing organic substances in the organic substance oxidizing apparatus,
In addition, it is not necessary to add an alkali agent for making the water to be treated alkaline, or the amount of the alkali agent can be reduced.

In the apparatus for producing ultrapure water of the present invention, an ion exchange apparatus using at least an anion exchange resin can be provided downstream of the organic matter oxidation apparatus. In this way, even when the organic matter is not decomposed into carbon dioxide in the organic matter oxidizer, if the organic matter is decomposed into the organic acid which is an ionic substance in the organic matter oxidizer, the organic matter is used in the subsequent ion exchanger. Since the above-mentioned ionic substance is removed by the anion exchange resin used, organic substances are efficiently removed as a whole. In this case, p in the organic oxidation device
By adjusting the amount of H or ozone added, organic substances may be intentionally decomposed into organic acids without being decomposed into carbon dioxide. As a result, the amount of use of the alkali agent and the amount of ozone added can be reduced, so that the running cost can be reduced. Examples of the ion exchange apparatus include, for example, an anion exchange apparatus using only an anion exchange resin, a mixed bed pure water production apparatus combining an anion exchange resin and a cation exchange resin, and a double bed pure water production. It is possible to use an apparatus, a two-bed, three-tower type pure water production apparatus, or the like.

In the ultrapure water producing apparatus of the present invention, an ozone decomposing means for decomposing ozone in the water to be treated can be provided downstream of the organic matter oxidizing apparatus. Thereby, it is possible to prevent ozone remaining in the treated water of the organic matter oxidizing apparatus from adversely affecting the subsequent ion exchange apparatus and the like. Examples of the ozone decomposing means include a means for reducing the decomposition of ozone by passing treated water through activated carbon, and a means for reducing and decomposing ozone by injecting a reducing agent into the treated water. The ozone decomposing means is preferably provided immediately after the organic oxidizing device in order to prevent ozone from adversely affecting the subsequent device.

In the apparatus for producing ultrapure water of the present invention, a deaerator can be provided downstream of the organic matter oxidizer. The deaerator is originally a device for removing dissolved oxygen in the water to be treated, but also removes a part of volatile organic substances present in the water to be treated when the dissolved oxygen is removed from the water to be treated. Therefore, by providing the deaerator on the downstream side of the organic matter oxidizing apparatus, it is possible to obtain treated water having a further reduced organic matter concentration. As the deaerator, for example, a vacuum deaerator, a membrane deaerator or the like can be used. Membrane deaerator is a system in which water to be treated flows into one chamber partitioned by a gas-permeable membrane, and the other chamber is decompressed to allow gas contained in the water to be treated to pass through the gas-permeable membrane to the other chamber. It is a device that moves and removes.

Further, in the apparatus for producing ultrapure water of the present invention, an activated carbon filter for pretreatment is provided upstream of the reverse osmosis membrane apparatus, or a reverse osmosis membrane apparatus (second) is provided downstream of the organic matter oxidation apparatus. Or a reverse osmosis membrane device).
When the second reverse osmosis membrane device is provided, the concentration of organic substances in the treated water can be further reduced.

In the apparatus for producing ultrapure water of the present invention, a reverse osmosis membrane apparatus and an organic matter oxidizing apparatus are installed in a pure water wastewater recovery system of a wastewater recovery system, and the permeated water of the reverse osmosis membrane apparatus is treated by the organic matter oxidizing apparatus. And the concentrated water of the reverse osmosis membrane device can be introduced into the wastewater recovery system for waste water or the wastewater treatment system of the wastewater recovery system. Also, without providing a wastewater treatment system, the ultrapure water production apparatus of the closed system that is reused as ultrapure water raw water or miscellaneous water without discharging the ultrapure water drainage from the place of use, Similarly, the reverse osmosis membrane device and the organic matter oxidizing device can be installed in the wastewater recovery system for pure water, and the concentrated water of the reverse osmosis membrane device can be introduced into the wastewater recovery system for miscellaneous water. Doing the above,
Organic substances can be highly removed from the water to be treated in the wastewater recovery system for pure water, so that highly purified ultrapure water can be obtained by reusing the treated water and concentration of the reverse osmosis membrane device. Effective use of water or appropriate treatment can be achieved.

[0026]

FIG. 1 is a partially omitted flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention. FIG.
22 is a pretreatment system, 24 is a primary pure water system,
Reference numeral 26 denotes a pure water drainage recovery system. The pretreatment system 22 is provided with a coagulation filtration device (F) and an activated carbon filtration device (CF). In the primary pure water system 24, from the upstream side to the downstream side, an activated carbon filtration device (CF) 28, a two-bed three-column pure water production device (2B3T) 30, a mixed-bed pure water production device (MBP)
32, vacuum degassing tower (VD) 34 and reverse osmosis membrane device (R
O) 36 are sequentially installed. In the recovery system 26, an activated carbon filtration device (CF) 38, O
An anion exchange device (WA) 40, a reverse osmosis membrane device (RO) 42, and an organic matter oxidation device 44 using an H-type weakly basic anion exchange resin are sequentially installed.

In the present apparatus, the treated water in the pretreatment system 22 and the pure water drainage recovery system 26 is introduced into the primary pure water system 24 after being stored in a tank 46. The treated water in the primary pure water system 24 is sent to a secondary pure water system (not shown), and the ultrapure water produced in the secondary pure water system is supplied to a place of use (not shown). The wastewater generated by using ultrapure water at the place of use is treated in a pure water wastewater recovery system 26, and then treated in a tank 46.
And recycled as part of the raw water of the ultrapure water production equipment.

In the ultrapure water production apparatus of the present embodiment, the activated carbon filtration apparatus 28 of the primary pure water system 24 corresponds to the ozone decomposing means on the downstream side of the above-mentioned organic substance oxidizing apparatus, and is a two-bed three-column pure water production apparatus. 30 and the mixed-bed type pure water production apparatus 32 correspond to the ion exchange apparatus on the downstream side of the organic matter oxidization apparatus described above,
The vacuum degassing tower 34 corresponds to a deaerator on the downstream side of the organic matter oxidizing device described above, and the reverse osmosis membrane device 36 corresponds to the second reverse osmosis membrane device described above. However, these ozone decomposing means, the ion exchange device, the degassing device, and the second reverse osmosis membrane device may be separately provided in the pure water wastewater recovery system 26, thereby reducing the load on the primary pure water system 24. Can be lower.

In the ultrapure water production apparatus of this embodiment, wastewater from the place of use is treated in the pure water wastewater recovery system 26 and the primary pure water system 24 as follows. First, activated carbon filter 3
After a pretreatment is performed in step 8 to remove hydrogen peroxide and the like that degrade the reverse osmosis membrane, water is passed through the anion exchange device 40,
Here, the anionic impurities are removed by the OH type weakly basic anion exchange resin, and the outlet water becomes alkaline. Next, after a part of organic matter and anionic impurities are removed by the reverse osmosis membrane device 42, the organic matter oxidizing device 44 is removed.
Where the organic matter is oxidatively decomposed.

The organic substance oxidizing apparatus 44 has a structure shown in FIG. That is, in FIG. 2, reference numeral 50 denotes a line through which the water to be treated flows in the pure water drainage recovery system 26, and the alkali injection device 52 and the ozone supply device 54 are connected to the line 50. Alkali injection device 5
A pH measuring unit (not shown) is provided slightly behind a connecting portion 58 between the injection tube 56 and the line 50 of the second sample.
The pH of the water to be treated is measured by the H measuring unit, and the measurement result is output as an electric signal to the alkali injecting device 52, based on which the amount of alkali to be injected into the water to be treated is automatically controlled.

As the ozone supply device 54, an ozone generation device having an ozone generation mechanism or an ozone tank filled with an ozone-containing gas produced by the ozone generation device is used. A gas-liquid stirring / mixing device 62 (for example, a line mixer or an ozone dissolving pump) is connected to the supply pipe 60 of the ozone supply device 54, and the gas-liquid stirring / mixing device 62 is connected to the line 50. A predetermined length of the line 50 on the outlet side of the gas-liquid stirring and mixing device 62 is configured as a reaction tube portion 66 in which an oxidative decomposition reaction of an organic substance is performed.

In the organic matter oxidizing apparatus 44 of this embodiment, first, alkali is injected into the water to be treated flowing through the line 50 from the alkali injecting apparatus 52 so that the pH of the water to be treated is 9.7 or more, preferably 9.7 to 11 .0. Next, ozone is supplied to the water to be treated from the ozone supply device 54, the ozone and the water to be treated are stirred and mixed by the gas-liquid stirring and mixing device 62, and most of the ozone is dissolved in the water to be treated. Here, the amount of ozone added to the water to be treated is adjusted to 3 to 40 ppm, preferably 7 to 30 ppm. In the to-be-treated water, the oxidative decomposition reaction of the organic matter rapidly proceeds in the reaction tube section 66. The treated water obtained by the end of the oxidative decomposition reaction is supplied to the primary pure water system 24 via the tank 46 together with the treated water of the pretreatment system 22.

In the primary pure water system 24, the water to be treated is first passed through an activated carbon filtration device 28, where dissolved ozone in the water to be treated is decomposed, and then decomposed to carbon dioxide by an organic oxidation device 44. Ion substance (organic acid) that did not exist is a two-bed three-column pure water production system 30 and a mixed-bed pure water production system 3
It is removed by the anion exchange resin used in Step 2. Next, removal of dissolved oxygen and removal of a small amount of organic substances are performed in the vacuum degassing tower 34, and further, remaining impurities are removed in the reverse osmosis membrane device 36. In addition, acetone remains in the treated water of the organic matter oxidizing apparatus 44, and this is the pure water producing apparatus 30,
Even when the acetone has passed through, the acetone is volatile and can be removed by the vacuum degassing tower 34.

FIGS. 3 to 5 are flow charts showing one embodiment of the ultrapure water production apparatus according to the present invention. FIG.
5 is an activated carbon filtration device (C
F) a primary pure water system equipped with a two-bed three-column pure water production system (2B3T), a mixed-bed pure water production system (MBP), a vacuum degassing tower (VD) and a reverse osmosis membrane device (RO); Tank (T
K), an ultraviolet sterilizer (UV _st ), a mixed-bed type cartridge polisher (CP), and a secondary pure water system equipped with an ultrafiltration membrane device (UF).

In the apparatus shown in FIGS. 3 to 5, as a wastewater recovery system for treating wastewater generated by using ultrapure water at the place of use, no treatment is performed according to the cleanliness of the wastewater. Route to return directly to primary pure water system, route to return to primary pure water system after applying appropriate treatment (pure water wastewater recovery system), route to apply appropriate treatment and then supply it as utility water to utility equipment (for utility water) (Wastewater recovery system) and a route (wastewater treatment system) for discharging after appropriate treatment. The criteria for separating the ultrapure water drained from the place of use into the above-mentioned routes are, for example, as shown in Table 1.
The classification is performed by the classification mechanisms (1) to (3).

[0036]

[Table 1]

In the apparatus shown in FIGS. 3 and 4, an activated carbon filter (C) is provided in the pure water wastewater recovery system from the upstream side to the downstream side.
F), an anion exchange device (WA) using a weakly basic anion exchange resin in the OH form, a reverse osmosis membrane device (RO), and an organic matter oxidation device are sequentially installed. The treatment of waste water in the pure water waste water recovery system of the apparatus of FIGS. 3 and 4 is the same as that of the apparatus of FIG. Further, in the apparatus of FIG. 3, the concentrated water of the reverse osmosis membrane device of the pure water waste water recovery system is introduced into the waste water waste water recovery system, and in the apparatus of FIG. 4, the concentrated water is introduced into the waste water treatment system. is there. When the cleanness of the concentrated water of the reverse osmosis membrane device is relatively high, the concentrated water is introduced into the wastewater drainage recovery system as shown in FIG. When the concentration is relatively low, the concentrated water may be treated and discharged in a wastewater treatment system as in the apparatus shown in FIG. The apparatus of FIG. 5 is obtained by omitting an anion exchange apparatus (WA) from the apparatus of FIG.

As another embodiment of the present invention, in the apparatus shown in FIG. 5, instead of a reverse osmosis membrane apparatus (RO), OH
Anion exchange device (W) using an anion exchange resin
A) may be provided, and the cleaning wastewater may be treated in the order of CF → WA → organic matter oxidation apparatus.

[0039]

EXAMPLES Example 1 Activated carbon filtration device (CF), anion exchange device (WA),
First reverse osmosis membrane device (RO), organic matter oxidation device, activated carbon filtration device (CF), two-bed three-column pure water production device (2B3
T), mixed bed pure water production equipment (MBP), vacuum degassing tower (V
D) and a second reverse osmosis membrane device (RO) were connected in this order, and the wastewater generated by using ultrapure water was flown to treat the wastewater. The wastewater having a TOC concentration shown in Table 2 was used. In this case, in the organic matter oxidizing device 44, sodium hydroxide is added to the water to be treated from the alkali injection device 52 to adjust the pH of the water to be treated to the value shown in Table 2, and then the gas-liquid stirring and mixing device 62 Ozone was added to the water to be treated so that the amount of ozone added to the water to be treated became the value shown in Table 2.

As the gas-liquid stirring and mixing device 62, an ozone dissolving pump was used. In addition, an anion exchange device (W
As the anion exchange resin of A), Amberlite (registered trademark, hereinafter the same) IR which is a weakly basic anion exchange resin
A-94S OH type is used, and a polyamide composite membrane ES-10 manufactured by Nitto Denko Corporation is used as a reverse osmosis membrane of the first and second reverse osmosis membrane devices (RO). As the cation exchange resin for the water producing apparatus (2B3T), Hmber of Amberlite IR-124, which is a strongly acidic cation exchange resin, is used.
As the form and anion exchange resin, OH form of Amberlite IRA-402BL which is a strongly basic anion exchange resin is used, and as the ion exchange resin of the mixed bed type pure water production apparatus (MBP), H form strong acid cation is used. Amberlite ESG4 obtained by mixing an ion exchange resin and a strong basic anion exchange resin in the OH form was used. Vacuum deaerator (VD) has a degree of vacuum of 22
Driving in Torr. Table 2 shows the measurement results of the TOC concentration of the outlet water of each device.

Example 2 Example 1 was repeated using the same apparatus as used in Example 1 except that the first reverse osmosis membrane apparatus was omitted from the wastewater recovery system for pure water of the apparatus used in Example 1. Wastewater generated by using ultrapure water was treated in the same manner as described above. Table 2 shows the results.

[0042] Using the same equipment as non-excluding the reverse osmosis unit of the anion-exchange device and the first pure water waste water recovery system for the apparatus used in Comparative Example 1 was used in Example 1 The wastewater generated by using ultrapure water was treated in the same manner as in Example 1. Table 2 shows the results.

[0043]

[Table 2]

As shown in Table 2, after the water to be treated containing an organic substance was treated with a reverse osmosis membrane apparatus or an anion exchange apparatus, the permeated water of the reverse osmosis membrane apparatus or the treated water of the anion exchange apparatus was treated with an alkaline substance in an organic substance oxidation apparatus. It was confirmed that when ozone was added under the conditions, the TOC removal efficiency in the organic matter oxidation device and the subsequent ion exchange device was improved. However, when the ozone concentration or the pH of the water to be treated is low during the treatment in the organic matter oxidizing apparatus (Test Nos. 5 to 7), the TOC in the organic matter oxidizing apparatus and the subsequent ion exchange apparatus is not sufficient.
The removal efficiency was reduced. It is considered that the reason why the TOC removal efficiency in the subsequent ion exchange device was reduced was that the organic matter was not sufficiently oxidized in the organic matter oxidizing device and did not become an ionic substance.

[0045]

According to the first aspect of the present invention, in the reverse osmosis membrane device, anionic impurities that inhibit the oxidative decomposition reaction of organic matter in the organic matter oxidizing device are removed from the water to be treated, and the water in the water to be treated is removed. Since organic matter is considerably removed, the efficiency of removing organic matter in the organic matter oxidizing apparatus is improved. In addition, since the organic matter in the water to be treated is considerably removed by the reverse osmosis membrane device, the amount of ozone used in the organic matter oxidizing device can be reduced, and the size of the ozone generator can be reduced, and even if the pH is not so high. Since organic substances can be oxidatively decomposed, consumption of an alkali agent added to the water to be treated can be reduced.

According to the second aspect of the present invention, since the organic matter can be highly removed from the water to be treated in the pure water wastewater recovery system of the wastewater recovery system, the purified water can be reused to achieve high purity. Ultrapure water can be obtained, and effective use of the concentrated water of the reverse osmosis membrane device or appropriate treatment can be achieved.

According to the third aspect of the present invention, anionic impurities that inhibit the oxidative decomposition reaction of organic substances in the organic substance oxidizing apparatus can be removed to a higher degree, and the efficiency of removing organic substances in the organic substance oxidizing apparatus can be further enhanced. In addition, since the outlet water of the anion exchange device becomes alkaline, it is not necessary to add an alkaline agent for making the water to be treated alkaline, or it is possible to reduce the amount of the alkaline agent.

According to the fourth aspect of the present invention, it is possible to remove anionic impurities from the water to be treated, thereby improving the efficiency of removing organic substances in the organic substance oxidizing apparatus, and furthermore, to make the water to be treated alkaline. This makes it unnecessary to add an agent or reduces the amount of the agent added.

According to the fifth aspect of the present invention, even when the organic matter is not decomposed into carbon dioxide in the organic matter oxidizing apparatus,
If the organic substance is decomposed into an ionic substance such as an organic acid in the organic substance oxidizing apparatus, the ionic substance is removed in the subsequent ion exchange apparatus, so that the organic substance is efficiently removed as a whole.

According to the sixth aspect of the present invention, it is possible to prevent dissolved ozone remaining in the treated water of the organic matter oxidizing apparatus from adversely affecting a subsequent apparatus, for example, an ion exchange resin of an ion exchange apparatus.

According to the seventh aspect of the present invention, when the dissolved gas is removed from the water to be treated by the deaerator, volatile organic substances present in the water to be treated are also removed, so that the concentration of the organic substance is further reduced. Treated water can be obtained.

According to the invention of claims 8 to 10, the oxidative decomposition of organic substances in the organic substance oxidizing apparatus can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is a partially omitted flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention.

FIG. 2 is a flowchart showing an organic oxidation apparatus of the ultrapure water production apparatus shown in FIG.

FIG. 3 is a flowchart showing an embodiment of the ultrapure water production apparatus according to the present invention.

FIG. 4 is a flowchart showing an embodiment of the ultrapure water production apparatus according to the present invention.

FIG. 5 is a flowchart showing an embodiment of the ultrapure water production apparatus according to the present invention.

FIG. 6 is a graph showing the relationship between the pH of water to be treated and the rate of oxidative decomposition of organic substances.

FIG. 7 is a flowchart showing an example of a conventional ultrapure water production apparatus.

[Explanation of symbols]

 22 Pretreatment system 24 Primary pure water system 26 Pure water wastewater recovery system 28 Activated carbon filtration device 30 Two-bed three-tower pure water production device 32 Mixed-bed pure water production device 34 Vacuum deaeration tower 36 Reverse osmosis membrane device 38 Activated carbon filtration Equipment 40 Anion exchange equipment 42 Reverse osmosis membrane equipment 44 Organic matter oxidation equipment

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/20 C02F 1/20 A 1/42 1/42 A 1/44 1/44 J 1/58 1/58 H 1 / 78 1/78

Claims (10)

[Claims] 1. A reverse osmosis membrane device for passing water to be treated containing an organic substance, and an organic substance contained in the permeated water is oxidized by adding ozone to the permeated water of the reverse osmosis membrane apparatus under alkaline conditions. An apparatus for producing ultrapure water, comprising: an apparatus for oxidizing organic matter that decomposes. 2. An ultrapure water production apparatus comprising: a primary pure water system for processing raw water to produce primary pure water; a secondary pure water system for treating primary pure water to produce ultrapure water; A wastewater recovery system that processes wastewater generated by using ultrapure water produced in a pure water system at the place of use and returns the wastewater to the primary pure water system, and comprises a reverse osmosis membrane device and an organic matter oxidation device. The system is installed in a pure water drainage recovery system, and the permeated water of the reverse osmosis membrane device is treated by an organic matter oxidizer and introduced into the primary pure water system.
The ultrapure water production apparatus according to claim 1, wherein the concentrated water of the reverse osmosis membrane device is introduced into a wastewater recovery system for wastewater or a wastewater treatment system of the wastewater recovery system. 3. The anion exchange device according to claim 1, wherein an anion exchange device using an OH type anion exchange resin is provided upstream of the reverse osmosis membrane device or between the reverse osmosis membrane device and the organic matter oxidation device. Ultrapure water production equipment. 4. An anion exchange device using an OH type anion exchange resin in place of the reverse osmosis membrane device, wherein water to be treated containing an organic substance is treated with the anion exchange device, The ultrapure water production apparatus according to claim 1, wherein the organic matter contained in the treated water of the exchange unit is oxidatively decomposed by an organic matter oxidation unit. 5. The ultrapure water production apparatus according to claim 1, wherein an ion exchange apparatus using at least an anion exchange resin is provided downstream of the organic matter oxidation apparatus. 6. An ozone decomposing means for decomposing ozone in the water to be treated is provided downstream of the organic matter oxidizing apparatus.
The ultrapure water production apparatus according to any one of the above. 7. The ultrapure water production apparatus according to claim 1, wherein a deaeration device is provided downstream of the organic matter oxidation device. 8. The apparatus for oxidizing organic matter, wherein ozone is added to the water to be treated by gas-liquid stirring and mixing means.
The ultrapure water production apparatus according to any one of claims 1 to 7. 9. The organic matter oxidizer according to claim 1, wherein the ozone is added to the water to be treated under alkaline conditions in which the pH of the water to be treated is 9.7 or more. Pure water production equipment. 10. The organic matter oxidation apparatus according to claim 1, wherein the ozone is added to the water to be treated so that the amount of ozone added to the water to be treated is 3 to 40 ppm.
The ultrapure water production apparatus according to the paragraph.