JPH1157753A - Removing method of toc component and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rational removing method of a TOC component and a compact production device as to the production of water without substantially containing the TOC component. SOLUTION: In this device, a major part of a TOC component is oxidatively decomposed by an ozone/hydrogen peroxide method while keeping the pH of TOC component-containing water at an around neutral, the obtained treated water is further treated by an ozone/alkali treating method and/or an ozone/UV ray treating method rapid in a reaction rate to ionize a residual TOC component and to remove the ion in the obtained treated water. A feed rate of the ozone and the hydrogen peroxide to the treating system is controlled preferably by feeding back and monitoring the TOC value of the treated water from the system based on the TOC value. A waste ozone from the ozone/hydrogen peroxide treating system is preferably used as at least a part of the ozone to be used in the ozone/alkali treating system and the ozone/UV ray treating system and an ozone utilization rate is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for removing a TOC component, and more particularly to water containing substantially no TOC component.
For example, the present invention relates to a method and an apparatus for removing a TOC component for producing and recovering pure water and ultrapure water used in a cleaning process in the electronics industry.

[0002]

2. Description of the Related Art Properly combining ozone, hydrogen peroxide, ultraviolet light, various oxidation catalysts, and the like generates hydroxyl radicals having stronger oxidizing power than each of these individual oxidation means alone. Since these oxidizing means do not generate anything other than the oxygen element and the hydrogen element, the risk of secondary contamination is low, and the salt load in the subsequent processing is also low. Due to such characteristics, a hydroxyl radical is generated by an appropriate combination of the above-described various oxidation means or a combination of ozone and an alkali (alkaline is not an oxidizing agent, but a hydroxyl radical is generated by this combination). The TOC component in component-containing water (hereinafter sometimes referred to as “raw water”) is oxidized and decomposed to produce TOC, ultrapure water, etc. and to recover pure water and ultrapure water after use.
It is widely practiced to remove components.

[0003] As described above, by various combinations of the above-mentioned various oxidizing means and combinations of ozone and alkali,
Although hydroxyl radicals are commonly generated, each of these combinations has different characteristics.
For example, the combination of hydrogen peroxide and ultraviolet (UV) is a classic use, but usually requires a reaction time of several hours or more due to the slow reaction rate. The reaction rate of the combination of ozone and ultraviolet light (UV) is considerably high because the UV absorption by ozone is very high, but the initial cost and running cost (power cost and replacement cost of ultraviolet lamp) due to the ultraviolet irradiation device Both) will increase. The combination of ozone and alkali has a high reaction rate and low running cost. However, when a high concentration of TOC component is present due to the reaction on the alkali side, carbonate ion (CO ₃ ²⁻ ) or bicarbonate ion (HCO 3
₃ ^-) The radical scavengers according to undergo reaction inhibition (the alkaline side, such as, if the carbon dioxide is one of the degradation products of TOC components is present as carbonate ion and bicarbonate ion, there is a high concentration TOC components Increases the amount of carbon dioxide generated). On the other hand, the combination of ozone and hydrogen peroxide slightly reduces the reaction rate, but has a relatively wide range of use because it is less affected by radical scavengers and is economically advantageous. Note that carbonate ions have a greater effect as radical scavengers than bicarbonate ions.

Further, in any of the above-mentioned hydroxyl radical generating mechanisms, since an organic acid is generated as an intermediate product, the hydroxyl radical generating mechanism further substantially completely oxidizes and decomposes to carbon dioxide and water to obtain TO TO.
Rather than removing the C component substantially completely, as an economical method, a portion of the generated organic acid that is not decomposed into carbon dioxide and water is left, and the remaining portion of the organic acid is removed by ion removal provided in the subsequent stage. It may be removed using a mechanism (for example, an ion exchange device or an ion removal device such as a reverse osmosis membrane (RO) device).

[0005]

As described above, the ozone / hydrogen peroxide method has been widely applied to the removal of TOC components because it is less affected by radical scavengers and has good economic efficiency. Due to the slowness, a large reactor (hydroxyl radical generator) is required when the TOC load is high. In the ozone / hydrogen peroxide method,
Since the efficiency of absorbing ozone into the hydrogen peroxide-containing water system is not sufficient, the ozone utilization rate is relatively poor, and this also imposes a burden on the subsequent exhaust ozone treatment step (eg, activated carbon treatment step or ultraviolet irradiation step).

The present invention solves the above-mentioned drawbacks of the prior art, and solves the above-mentioned drawbacks of the ozone / hydrogen peroxide method so that the TOC component in the TOC component-containing water is converted to ozone. It is intended to provide a method and an apparatus for removing a TOC component that can be dealt with by a compact reactor (hydroxyl radical generator) even when the TOC load is high, when decomposing and removing with hydrogen oxide. The aim is to increase the ozone utilization rate.

[0007]

The present invention has been completed based on the results of the following experiments conducted to solve the above-mentioned problems. That is, the present invention relates to TO
While maintaining the pH value of the water containing the C component around neutral, the T
TOC by supplying hydrogen peroxide and ozone to water containing OC component
The first step in which most of the components are decomposed, and the treated water obtained in the first step are further subjected to (1) ozone treatment under alkaline conditions and / or (2) ozone treatment under ultraviolet irradiation. T comprising a second step of ionizing at least substantially all of the remaining TOC component.
Method for removing OC component, and pH of water containing TOC component
A first treatment device for supplying hydrogen peroxide and ozone to the TOC component-containing water to decompose most of the TOC component while maintaining the value near neutral, and treated water obtained from the first treatment device In addition, a second treatment apparatus for performing (1) ozone treatment under alkaline conditions and / or (2) ozone treatment under ultraviolet irradiation to ionize at least substantially all of the remaining TOC components is included. A TOC component removing apparatus is provided. When (1) ozone treatment under alkaline conditions and (2) ozone treatment under ultraviolet irradiation are used in combination, the treatment may be performed in two stages, and in this case, the apparatus may be provided in two stages. Further, “near neutral” in the first step (first processing apparatus) generally means a pH value in a range of 6.0 to 8.0, and preferably a pH value in a range of 6.5 to 7.8. pH value.

[0008] The treated water obtained by the present invention is, for example,
When sent to the subsequent ultrapure water production step, the method of the present invention preferably further includes a third step of removing ions from the treated water obtained in the second step. It is preferable to further include an ion removing device for removing ions from the treated water obtained from the device.

According to the results of experiments conducted by the inventor, it has been found that in an ozone / hydrogen peroxide treatment system, oxidative decomposition of organic substances shows a primary reaction characteristic with respect to the TOC concentration (TOC value). Clogging, the reaction rate of the ozone / hydrogen peroxide method is low, especially in the low TOC concentration region. Therefore, most of the TOC component removal is carried out by the low-cost ozone / hydrogen peroxide method, and the remaining portion has a high reaction rate (1) ozone treatment under alkaline conditions and / or (2) ultraviolet irradiation. By performing the ozone treatment, it is possible to achieve effective TOC component removal with a more compact apparatus at a reasonable treatment cost. That is,
According to the above-described TOC component removal method (apparatus) of the present invention,
An excellent TOC component removing effect can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

According to the results of the experiment, it has been found that the reaction rate in the ozone / hydrogen peroxide method becomes extremely low when the TOC value of the treated water becomes 2.5 mg / L (liter) or less. Therefore, the target value of the TOC value of the treated water from the ozone / hydrogen peroxide treatment system is, for example, 1.0 to 3.0 mg /
L, preferably about 1.5 to 2.5 mg / L. It is preferable to control the amount of generated ozone so that the TOC value falls within such a range, and it is preferable to control the amount of added hydrogen peroxide in conjunction with the amount of generated ozone. In this case, the weight ratio of hydrogen peroxide / ozone is 0.2 /
Preferably it is 1 to 0.4 / 1.

In the second step of the TOC component ionization, which can efficiently treat the treated water from the ozone / hydrogen peroxide treatment system in the first step of oxidatively decomposing the TOC component,
The method of (1) ozone treatment under alkaline conditions and the method of (2) ozone treatment under ultraviolet (UV) irradiation can be used in the present invention. It is preferable to use the ozone gas discharged from the ozone / hydrogen peroxide treatment system in the first step as at least a part of the ozone used in the second step, since the utilization rate of ozone can be increased, and a general TOC source is used. (Type of organic substance as TOC component) When, for example, alcohols, organic acids, and the like are used as main TOC sources, ozone exhaust gas can be used without any trouble.

When there is a possibility that amines, ammonia and / or other compounds containing reduced nitrogen may be mixed into the raw water as a TOC source, (2) the ozone / alkaline treatment method is more preferable than the ozone / alkali treatment method. The UV treatment method is more appropriate. This is because on the alkaline side, these compounds consume ozone, for example, ammonia reacts with ozone under alkaline conditions to form nitric acid.

(1) When the ozone / alkali treatment method is applied to the second step, the treated water from the ozone / hydrogen peroxide treatment system in the first step is once aerated under acidic conditions, and the carbonate ion (CO 2 ₃ ^2-) and bicarbonate ion (HCO ₃ ^- is after removing the ozone / alkali treatment most of) the carbon dioxide, from the viewpoint of reducing the influence of a radical scavenger, preferably. As the alkali, for example, sodium hydroxide or potassium hydroxide can be used. Further, when (2) the ozone / UV treatment method is applied to the second step, hydrogen peroxide may be further supplied to this step.

TOC value of treated water (hereinafter sometimes referred to as “first treated water”) obtained by treating raw water in the first step (first treating apparatus) and entering the second step (second treating apparatus) Is a substantially constant value as described above. Therefore, based on the TOC value of the treated water (hereinafter sometimes referred to as “second treated water”) from the second step (second treating apparatus), Two processing equipment)
Although it is not particularly necessary to control the ozone supply amount and the alkali addition amount and / or the ozone supply amount and the output amount of the ultraviolet lamp in the above, it is needless to say that such control may be performed, and the TOC value of the second treated water may be controlled. It is preferable to perform such control in order to stabilize.

When such control is performed in the (1) ozone / alkali treatment system, the control of the alkali addition amount is preferably controlled by the pH value of the second treated water, rather than linked with the ozone supply amount. The pH of the second treated water is on the alkaline side, preferably 8 to 11, more preferably 8.5 to 1.
What is necessary is just to make it the value within the range of 0.5. In general, the higher the pH value, the higher the reaction rate. However, since the amount of alkali added is large, the subsequent stage of the ion removing device (such as an ion exchange resin treatment device or a reverse osmosis membrane device).
, The carbon dioxide ion and the bicarbonate ion, in particular, the ratio of existing as a carbonate ion increases, so that the action as a radical scavenger also increases.

When such control is performed in the (1) ozone / ultraviolet treatment system, it is preferable to control the supply amount of ozone and the output amount of the ultraviolet (UV) lamp in conjunction with each other. Clogging, proportional to
V lamp output amount / ozone supply amount ratio of 0.2 to 5 kw /
It may be controlled to be in kg-O _3. The ultraviolet lamp to be used may be a low-pressure mercury lamp having a main wavelength of 254 nm, or a main wavelength of 254 nm or 185 nm, or a high-pressure mercury lamp having a main wavelength of 365 nm, preferably a low-pressure mercury lamp having a main wavelength of 254 nm. Is used.

As a method of generating ozone, a silent discharge method,
Various methods such as a water electrolysis method can be used.

The second treated water from the second step (second treating device) avoids the adverse effect that the remaining oxidizing agent causes to deteriorate the materials such as the ion exchange resin and the reverse osmosis membrane used in the subsequent ion removing device. Therefore, it is usual to remove the remaining oxidizing agent before removing the ions. Examples of the method for removing the residual oxidant include activated carbon treatment, injection of a reducing agent (for example, sodium sulfite), ultraviolet irradiation, contact with a reduction catalyst (for example, a palladium-based catalyst), and the like. In addition, the apparatus is simple and preferable.

As mentioned above, the ozone / hydrogen peroxide method
In order to obtain a relatively high reaction rate in a high TOC concentration region, the raw water having a high TOC value is treated by the ozone / hydrogen peroxide method to remove most of the TOC component, and the resulting first treated water is subjected to Further, the processing speed is very high. (1) Ozone / alkali treatment and / or (2) ozone / ultraviolet (UV) treatment provide a more compact and more reasonable treatment system. be able to.

The ion can be removed using various ion exchange methods (apparatuses) or ion elimination methods (apparatuses) such as a reverse osmosis membrane (RO) method (apparatus).

Generally, the capacity of the processing apparatus (first processing apparatus + second processing apparatus) configured as described above is the capacity of the processing apparatus (reactor) in the case of ozone / hydrogen peroxide processing alone. 1/2 to 1/4 of The capacity of the second processing apparatus may be much smaller than that of the first processing apparatus, and may be 1/2 to 1/20 of the capacity of the first processing apparatus.
Usually, 1/3 to 1/10 is sufficient. Furthermore, since ozone is used in the ozone / alkali treatment and / or ozone / ultraviolet (UV) treatment in the second step, the ozone gas discharged from the ozone / hydrogen peroxide treatment device can be reused as an ozone source at least as a part thereof. Also, the load on the exhaust ozone gas treatment system can be significantly reduced. The ozone utilization rate of the ozone / hydrogen peroxide treatment apparatus is generally 75% to 85%, but the first treatment apparatus (ozone / hydrogen peroxide treatment method) and the second treatment apparatus [ozone / alkali treatment Method and / or ozone / ultraviolet (UV) treatment method], so that the ozone utilization rate is generally 9%.
It can be as high as 0% or more and, if desired, up to 95% or more.

[0023]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

FIG. 1 shows the apparatus used in the embodiment. This figure is also a system flow diagram showing an example of the apparatus of the present invention. The first reaction tank 101 is a reactor that treats TOC component-containing water as raw water and oxidizes and decomposes most of the TOC components in the raw water with hydrogen peroxide and ozone. Thus, raw water is sent from the raw water line 141. The TOC value of a part of the first reaction tank treated water from the first reaction tank 101 is measured by the TOC meter 120, and a control signal 122 is transmitted from the PID controller 121 based on the TOC value, and the ozone generator 130 Along with the control, a hydrogen peroxide pump control signal 123 linked to the ozone generation amount is used to control the hydrogen peroxide pump 150. The ozonized gas generated by the ozone generator 130 is supplied through the ozonized gas line 131 to the first reaction tank 10.
Injected into 1. In Examples and Comparative Examples, the first reaction tank 10
Although the ozone dissolution in 1 was performed through a diffuser (a diffuser plate), other means such as an ejector and an in-line mixer can be used. Hydrogen peroxide is supplied to the first reaction tank 101 through the hydrogen peroxide line 151 by the hydrogen peroxide pump 150. Most of the other water in the first reaction tank treated water is supplied to the second reaction tank 161 through the first reaction tank treated water line 110, where it is treated by a treatment means (ozone / alkali or ozone / UV) having a high reaction rate. Is done. As the ozone source for this treatment means, ozone gas discharged from the first reaction tank is used. The ejector 165 provided in the circulating water line 163 passes through the ozone gas line 133 discharged from the first reaction tank. The ozone discharged from the first reaction tank is dissolved in the treated water sent by 162, and the treated water in which ozone is dissolved is returned to the second reaction tank 161 for use. In the example and the comparative example, the above-described ejector 165 was used for dissolving ozone in the second reaction tank 161, but other means such as a diffuser and a line mixer may be used. The treated water of the second reaction tank from the second reaction tank 161 is supplied to the activated carbon tower 11 through the treated water line 166 of the second reaction tank.
1 and the remaining oxidizing agents (hydrogen peroxide and ozone) are decomposed, and the treated water subjected to the activated carbon treatment is sent to the ion exchange resin tower 112 where organic acids and the like are removed by ion exchange. And flows out to the ion-exchanged treated water line 113 as treated water after ion exchange. Note that 16
Reference numeral 4 denotes a second reaction tank exhaust gas discharge pipe.

Example 1 In the apparatus shown in FIG. 1, a flow rate of 100 L / hr and p
H7.5, raw water having a TOC value of 6 mg / L [TOC source: isopropyl alcohol (IPA)] is first passed through a first reaction tank 101 having a capacity of 50 L and treated by an ozone / hydrogen peroxide method. The treated water was supplied to a 5 L capacity second reaction tank. Ozone was generated by a silent discharge method. The amount of ozone supplied to the first reaction tank 101 was set to about 15 times (weight) the amount of the TOC component in the raw water, and the amount of hydrogen peroxide supplied to the first reaction tank 101 by the hydrogen peroxide pump 150 was equal to the amount of ozone. It was about 0.31 times (weight). First reaction tank 101
Was dissolved through a diffuser.
In the second reaction tank 161, a circulation pump 162
The treated water is circulated, and an ejector 165 is attached to the circulating water line 163.
The discharged ozone gas from No. 1 was dissolved in the treated water by the ejector 165. Sodium hydroxide as an alkali was supplied to the second reaction tank 161, and the supply amount was controlled such that the pH value of water in the second reaction tank 161 was maintained at about 9.5.

The TOC value of the treated water 110 oxidized in the first reaction tank 101 is calculated using the sea bath 810 type TO
The measurement is performed on-line by a C meter 120 (manufactured by Seabus Corp. (USA)), a measurement signal from the TOC meter 120 is sent to a PID controller 121, and the amount of ozone generated is controlled by the PID controller 121 and hydrogen peroxide / ozone is used. Weight ratio = 0.
The hydrogen peroxide pump 150 was controlled so as to be 31/1, and the amount of generation of hydroxyl radicals in the first reaction tank 101 was automatically controlled by both.

The treated water from the second reaction tank 161 is treated in the activated carbon tower 111 to decompose oxidants (O ₃ , H ₂ O ₂ ).
Ionic organic substances (organic acids) were removed by the ion exchange resin tower 112. Table 1 shows the results of the above-described TOC component removal treatment performed by changing the HRT (hydraulic residence time) in the first reaction tank 101. The data in the column of “TOC after ion exchange” of “O ₃ / H ₂ O ₂ treatment” are the values in the first reaction tank 1
01, a part of the treated water immediately after the O ₃ / H ₂ O ₂ treatment is sampled, treated with the same activated carbon as the activated carbon tower 111, and the oxidizing agent (O ₃ , H ₂ O ₂ ) is decomposed. Tower 1
12 is TOC data of treated water obtained by treatment with the same ion exchange resin as in FIG.

[0028]

[Table 1]

Comparative Example 1

For comparison, the HR in the first reaction vessel 101 was also reduced by the TOC component removal treatment using only the ozone / hydrogen peroxide method.
The test was performed while changing T (hydraulic residence time). In this comparative example, the treated water from the first reaction tank 101 was
1 through an activated carbon tower similar to the activated carbon tower 111 to decompose the oxidizing agents (O ₃ , H ₂ O ₂ ), and then convert the ionic organic matter ( Organic acid) was removed. Table 2 shows the results.

[0031]

[Table 2]

Example 2 Example 1 was repeated except that the treatment in the second reaction tank 161 was performed by the ozone / ultraviolet method instead of the ozone / alkali method.
Similarly, the TOC component removal treatment was performed under substantially the same conditions. The irradiation amount of the ultraviolet rays (UV) was set to 0.2 kWh / m ³ as the output amount of the UV lamp. Since the alkali was not used, the pH value of the water in the second reaction tank 161 was not controlled, and was about 4 to 5. Table 3 shows the result of the TOC component removal processing.

[0033]

[Table 3]

As can be seen from Tables 1, 2 and 3, the ozone / hydrogen peroxide method alone required about 1.5 hours or more of HRT to achieve almost the same treated water quality (TOC value). On the other hand, in the combination of the ozone / hydrogen peroxide method and the ozone / alkali method or the ozone / UV method, the HRT
It took only about 0.5 hours (second reaction tank 161).
Is 1/10 of the capacity of the first reaction vessel 101, and the HRT in the second reaction vessel 161 is almost negligible). Therefore, according to the method of the present invention, it was found that the TOC component removing device can be made compact. Also, the ozone utilization rate was 78 to 78 in the ozone / hydrogen peroxide method alone.
Although the ozone utilization rate was 82%, the combined use of the ozone / hydrogen peroxide method and the ozone / alkali method or the ozone / UV method was 93% or more. I understood.

[0035]

According to the present invention, in the ozone / hydrogen peroxide treatment system of the water containing the TOC component, the decomposition of the organic matter is carried out by the TOC concentration (TOC concentration).
Value) was found to exhibit first order reaction characteristics. Therefore, the reaction rate of the ozone / hydrogen peroxide method is low particularly in a low TOC concentration region. Therefore, most of the TOC component removal is carried out by the ozone / hydrogen peroxide method with low cost and low salt load, and the remaining part is treated with a high reaction rate (ozone / alkali treatment method and / or ozone / ultraviolet treatment method). According to the method for removing TOC components of the present invention, effective TOC removal can be achieved with a more compact apparatus at a reasonable processing cost.

[Brief description of the drawings]

FIG. 1 is a system flow diagram showing one example of a TOC component removing apparatus of the present invention used in an embodiment.

[Explanation of symbols]

 Reference Signs List 101 first reaction tank 110 first reaction tank treated water line 111 activated carbon tower 112 ion exchange resin tower 113 ion exchange treated water line 120 TOC meter 121 PID controller 122 control signal 123 hydrogen peroxide pump control signal 130 ozone generator 131 Ozonized gas line 133 First reaction tank exhaust ozone gas line 140 Raw water pump 141 Raw water line 150 Hydrogen peroxide pump 151 Hydrogen peroxide line 161 Second reaction tank 162 Circulation pump 163 Circulating water line 164 Second reaction tank exhaust gas discharge pipe 165 Ejector 166 Second reaction tank treated water line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/78 C02F 1/78

Claims (8)

[Claims] 1. A first step of supplying hydrogen peroxide and ozone to the TOC component-containing water to decompose most of the TOC component while maintaining the pH value of the TOC component-containing water near neutral.
And (1) the treated water obtained in the first step.
Removing the TOC component, comprising a second step of performing ozone treatment under alkaline conditions and / or (2) ozone treatment under ultraviolet irradiation to ionize at least substantially all of the remaining TOC component. Method. 2. The method for removing a TOC component according to claim 1, further comprising a third step of removing ions from the treated water obtained in the second step. 3. The amount of ozone supplied in the first step is controlled by the TOC value of the treated water obtained in the first step. Preferably, the amount of hydrogen peroxide supplied in the first step is also linked with the amount of ozone supplied. 3. The control according to claim 1, wherein
3. The method for removing a TOC component according to item 1. 4. The method for removing a TOC component according to claim 1, wherein at least a part of the ozone used in the second step is exhausted ozone gas generated in the first step. . 5. A first treatment device for supplying hydrogen peroxide and ozone to the TOC component-containing water to decompose most of the TOC component while maintaining the pH value of the TOC component-containing water near neutrality, Further, the treated water obtained from the first treatment apparatus is further subjected to (1) ozone treatment under alkaline conditions and / or (2) ozone treatment under ultraviolet irradiation to remove substantially all of the remaining TOC components. An apparatus for removing a TOC component, comprising at least a second processing apparatus for ionizing. 6. The TOC component removing device according to claim 5, further comprising an ion removing device for removing ions from treated water obtained from the second treating device. 7. The supply amount of ozone in the first treatment device is controlled by a TOC value of treated water obtained from the first treatment device. Preferably, the supply amount of hydrogen peroxide in the first treatment device is also controlled by the ozone supply amount. 6. The apparatus according to claim 5, further comprising a feedback control mechanism for controlling the quantity in conjunction with the quantity.
Or a device for removing a TOC component according to 6. 8. An exhaust ozone gas supply means for supplying exhaust ozone gas generated in the first processing apparatus as at least part of ozone used in the second processing apparatus to the second processing apparatus. Claim 5
8. The apparatus for removing a TOC component according to any one of claims 1 to 7.