JP2002126730A - Apparatus and method for treating wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for treating washing wastewater capable of effectively treating IPA, DMSO, TMAH, a surfactant or the like contained in washing wastewater in a semiconductor manufacturing process. SOLUTION: A treatment apparatus for treating washing wastewater of a semiconductor process is equipped with a liquid feed means 2 for pressurizing washing wastewater to feed the same, a cavitation generation means 3 for ejecting the pressurized treated liquid sent under pressure by the liquid feed means to generate cavitation in the pressurized treated liquid and at least one free radical generation accelerating means 5 provided to at least the front and rear of the cavitation generation means and accelerating the generation of OH free radicals in the liquid to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning wastewater treatment apparatus and method for removing TOC components in cleaning wastewater discharged in a semiconductor manufacturing process, and more particularly, to recovery of a semiconductor manufacturing process using cavitation. T in drainage
It is designed to efficiently remove the OC component with low energy.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a large amount of ultrapure water is used for cleaning, and the recovery and reuse of cleaning wastewater is widely performed from the viewpoints of reducing the addition to the environment and effectively utilizing water resources. ing.

In a cleaning step in a semiconductor manufacturing process, TOC components such as alcohols such as isopropyl alcohol (hereinafter referred to as IPA), dimethyl sulfoxide (hereinafter referred to as DMSO), tetramethylammonium hydroxide (hereinafter referred to as TMAH), and a surfactant are contained. When the cleaning wastewater is collected and reused, it is necessary to remove the TOC component in the cleaning wastewater because it is mixed with the cleaning wastewater.

In general, as a method for treating wastewater containing IPA, DMSO, and TMAH, an aerobic biological treatment using activated sludge or microorganisms supported on a carrier is known.

However, in the case of biological treatment of DMSO-containing wastewater, it is difficult to keep the inside of the reaction tank under aerobic conditions, and odorous toxic gases such as methyl mercaptan and hydrogen sulfide are removed during the biodegradation process under anaerobic conditions. There is a problem that occurs. In order to solve this problem, various measures have been taken to keep the biological treatment tank under aerobic conditions.However, a part of the activated sludge floc or the inside of the carrier becomes an anaerobic condition, or the aerobic condition is stopped by stopping the device. When it was not possible to maintain the above, the above problem could not be avoided.

When an organic wastewater mixed with IPA, DMSO and TMAH is subjected to aerobic biological treatment, in many cases,
Only IPA is decomposed and DMSO and TMAH are not sufficiently decomposed. In order to sufficiently decompose DMSO and TMAH together with IPA, it is necessary to treat at a very low load, or to carry out wastewater containing IPA, wastewater containing DMSO,
It is necessary to completely separate the TMAH-containing wastewater, and to treat the IPA-containing wastewater with a normal load, and to treat the DMSO and TMAH-containing wastewater with a load 1/3 to 1/5 lower than the load of the IPA-containing wastewater. is there. This leads to an increase in the processing amount. In addition, biological treatment originally has a disadvantage that it takes a long time to perform the treatment.

At present, wastewater containing DMSO and TMAH is concentrated and then incinerated, which requires high costs for treatment. Furthermore, this method does not allow the reuse of treated wastewater.

[0008]

As described above, DMSO and TMAH contained in the collected wastewater in the semiconductor manufacturing process are time-consuming and require a large amount of dilution.
Since biological treatment is considered difficult, it is concentrated and incinerated at a high cost, but there are issues to be considered further in this incineration. For example, TM
With the incineration of AH, nitrogen contained in this order to be harmful NO _X gas cause air pollution, will require extensive exhaust gas treatment facilities. As described above, according to the conventional technology, the IOC, which is the TOC component in the cleaning wastewater in the semiconductor manufacturing process, is used.
It was difficult to collectively and efficiently oxidatively decompose washing wastewater containing PA, DMSO, and TMAH.

On the other hand, various attempts have been made to improve liquid quality by cavitation.
There are no reports that SO, TMAH, surfactants and the like were effectively treated.

[0010] For example, there is a method of generating cavitation by ultrasonic waves and thereby decomposing dioxin. However, generating cavitation by ultrasonic waves requires a large amount of energy. In addition, the generation of cavitation due to ultrasonic waves is local, so the decomposition efficiency is low, and the larger the device, the larger the portion where cavitation does not occur, making it difficult to increase the size of the device. ing.

[0011] Also, JP-A-2000-563 discloses that
Although a method of decomposing organic substances such as dioxin by cavitation generated by a nozzle is disclosed,
There are no reports that IPA, DMSO, TMAH, surfactants and the like were effectively treated. Note that Japanese Patent Laid-Open No. 2000-5
No. 63 describes that in order to decompose organic substances such as trichlorethylene and dioxin, an ejection pressure of 100 kg / mm ² (about 10 MPa) or more is required, which requires a large amount of energy. Then, it is the same as the method using cavitation by ultrasonic waves.

As described above, the cleaning wastewater in the semiconductor manufacturing process is treated by cavitation to obtain IPA, DMSO, T
There are no reports that MAH, surfactants and the like were effectively treated.

The present invention has been made in view of such a situation, and the present invention has been made in view of the fact that the I / O contained in the cleaning wastewater in the semiconductor manufacturing process.
It is an object of the present invention to provide a cleaning wastewater treatment method and a treatment apparatus capable of effectively treating PA, DMSO, TMAH, a surfactant, and the like.

[0014]

The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems. As a result, the cleaning wastewater in the semiconductor manufacturing process is pressurized by a pressurizing pump and passed through a nozzle, so that the cavitation treatment can be performed. The present inventors have found that TOC components can be collectively and efficiently removed by using ultraviolet irradiation or oxidizing agent addition treatment as a radical generation promoting means and repeating cavitation treatment as necessary, thereby completing the present invention. .

That is, the first aspect of the present invention is as follows.
In a processing apparatus for treating cleaning wastewater in a semiconductor manufacturing process, a liquid sending means for pressurizing and sending the cleaning wastewater, and injecting a pressurized processing liquid pressurized and sent by the liquid sending means, the injection Cavitation generating means for generating cavitation in the pressurized processing liquid, and at least one radical generation means provided at least one of before and after the cavitation generation means for promoting generation of OH radicals in the liquid to be processed A wastewater treatment apparatus comprising a promoting means.

According to a second aspect of the present invention, in the first aspect, there is further provided a circulating means for returning the cavitation processing liquid discharged from the cavitation generating means to an upstream side of the cavitation generating means. Wastewater treatment equipment.

According to a third aspect of the present invention, there is provided the wastewater treatment apparatus according to the first or second aspect, wherein the pressure by the liquid sending means is 1 MPa or less.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the radical generation promoting means includes at least one of an ultraviolet irradiation device and an oxidizing agent adding device. Wastewater treatment equipment.

According to a fifth aspect of the present invention, there is provided a processing method for treating cleaning wastewater in a semiconductor manufacturing process, wherein the cleaning wastewater is pressurized and jetted to generate cavitation in a pressurized processing solution and to perform the cavitation before and after the occurrence of cavitation. Wherein the generation of OH radicals is promoted in at least one of the liquids to be treated.

In the present invention, the liquid to be subjected to any one of the treatments of pressurizing and jetting for generating cavitation, adding an oxidizing agent for promoting the generation of radicals, and irradiating ultraviolet rays is called a liquid to be treated. In any one of the processes, a processing solution on which a specific process is performed or performed is referred to as follows, in particular, in distinction from a processing solution on which another process is performed. That is, the liquid to be processed before pressurization is “liquid before pressurization”, the pressurized liquid sent to the cavitation generating means is “pressurized liquid”, and the cavitation processing is performed by ejecting the pressurized liquid. The liquid that is performed and flows out of the cavitation generating means is referred to as “cavitation treatment liquid”.

FIG. 1 schematically shows a processing apparatus for carrying out the present invention. As shown in FIG. 1, the treatment apparatus of the present invention comprises a tank 1 storing cleaning wastewater containing a TOC component in a semiconductor manufacturing process, and a pressurizing and feeding liquid to be treated (in this case, raw water) from the tank 1. Pump 2 and pressure pump 2
And a cavitation nozzle 3 for generating cavitation by injecting the pressurized processing liquid pressurized in the above.

Here, minute cavities are generated in the pressurized processing liquid which is pressurized by the pressurizing pump 2 and jetted from the constricted portion of the cavitation nozzle 3, and TO is contained in the liquid to be processed.
Acts on the C component. That is, when the generated microcavity collapses, for example, 5000K, 500a
It is said that a high-temperature and high-pressure environment (hot spot) called tm occurs. In such a special space, "high-temperature combustion" or "direct thermal decomposition" occurs, so that organic matter is directly thermally decomposed. In addition, even water molecules can be oxidized by thermal dissociation.
It is considered that the TOC component in the liquid to be processed is decomposed by H radicals and H atoms, and the generated OH radicals are decomposed.

In the present embodiment, there is provided a circulation line 4 for returning at least a part of the cavitation processing liquid jetted from the cavitation nozzle 3 to the upstream side of the pressure pump 2 and jetting it again from the cavitation nozzle 3. The liquid to be processed that has passed through the cavitation processing liquid circulation line 4 is pressurized again by the pressure pump 2 and jetted from the cavitation nozzle 3. The circulating process performed using the circulating line 4 circulates all of the injected cavitation processing liquid, and performs a predetermined number of times, for example,
It may be repeated 2 to 50 times, or only a part of the cavitation treatment liquid may be circulated.
A switching means (not shown) such as a valve is provided at a branch point of the cavitation nozzle 3 with the circulation line 4 on the downstream side, and the liquid flows into the circulation line 4 at a predetermined ratio and a predetermined number of times. Or stop the inflow.

[0024] By such a circulation treatment, the TOC component in the liquid to be treated can be decomposed more efficiently. In this embodiment, the circulation is performed by the action of the pressurizing pump 2, but a pump for circulation may be separately provided.

In the present embodiment, an ultraviolet irradiation device 5 is provided for irradiating the cavitation treatment liquid ejected from the cavitation nozzle 3 with ultraviolet light. Such an ultraviolet irradiation device 5 is one of the radical generation promoting means of the present embodiment, and emits OH
The generation of radicals can be promoted, and the TOC component can be more completely decomposed.

The concentration of the TOC component in the washing wastewater used in the semiconductor manufacturing process used in the present invention is not particularly limited.
It can be particularly preferably used in the case of ppb to 20 ppm.

The capacity of the pressure pump 2 used in this embodiment is 1 MPa or less, and in this embodiment, the capacity is 0.4 MPa.

The cavitation nozzle 3 for injecting the pressurized processing liquid pressurized by the pressurizing pump 2 can efficiently generate cavitation in the pressurized processing liquid sent at a pressure of 1 MPa or less. The shape and structure are not particularly limited as long as they are not limited. That is, fine cavities can be effectively generated in the pressurized processing solution injected from the constricted portion of the cavitation nozzle 3, and a high-temperature and high-pressure environment in which water molecules are locally decomposed into OH radicals and H atoms due to the collapse of the fine cavities. What is necessary is just to cause it.

Further, the processing apparatus of the present embodiment includes an ultraviolet irradiation device 5 as a radical generation promoting means. The ultraviolet irradiation device 5 is not particularly limited, and a device including a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a hydrogen discharge tube, and the like can be used. The amount of ultraviolet light to be irradiated is not particularly limited, and may be appropriately selected depending on the type and concentration of the TOC component.
When treating the liquid to be treated containing 06 mg / liter of the TOC component, the amount is preferably 1 to 20 w · h.
As a result, not only the radical generation promoting action but also the effect of directly decomposing the remaining TOC component can be obtained.

The installation location of the ultraviolet irradiation device 5 can be selected as appropriate, such as upstream of the pressure pump 2, between the pressure pump 2 and the cavitation nozzle 3, downstream of the cavitation nozzle 3, and the circulation line 4. May be installed at any of the above.

As shown in FIG. 1, when the ultraviolet irradiation device 5 is provided on the downstream side of the cavitation nozzle 3, the decomposition process proceeds only by the cavitation. . By changing the standard of the UV lamp, space saving and power saving of the device can be expected, which is preferable.

The ultraviolet irradiation device 5 is preferably provided in the cavitation processing liquid circulation line 4 at a stage subsequent to the cavitation generating means.

FIG. 2 shows an example in which the ultraviolet irradiation device 5 is provided in the circulation line 4. By providing the ultraviolet irradiation device 5 in the circulation line 4 as described above, a synergistic effect of the cavitation treatment and the ultraviolet irradiation treatment is improved, and a trace amount of the TOC component can be effectively decomposed.

The circulation line 4 does not always need to be provided. By providing the circulation line 4, a small amount of TO
Although the C component can be effectively decomposed, it is not always necessary to provide a circulation line. FIG. 3 shows an example in which the circulation line is omitted.

Further, as another radical generation promoting means, a chemical injection tank for adding an oxidizing agent to the pre-pressurized solution before being pressurized by the pressurizing pump 2 may be provided.
This chemical injection tank is an oxidizing agent addition device as one of radical generation promoting means. When an oxidizing agent is injected from this chemical injection tank, the generation of OH radicals by cavitation is promoted, and the TOC component in the liquid to be treated is reduced. It can be decomposed more efficiently.

The location of the chemical injection tank, which is the oxidizing agent adding device, can be selected as appropriate.
Upstream, between the pressurizing pump 2 and the cavitation nozzle 3, downstream of the cavitation nozzle 3, or in the circulation line 4, but may be provided before the cavitation generator or in the circulation line 4. Is preferred,
In this case, the oxidizing agent is added to the untreated liquid to be treated, the pressure treatment liquid, or the cavitation treatment liquid in the circulation line.

Preferred examples of the oxidizing agent as a radical generation accelerator to be added to the liquid to be treated include hydrogen peroxide. The amount of the oxidizing agent to be added is appropriately selected according to the type, concentration, etc. of the TOC component in the liquid to be treated.
A range of 50 mg / L is preferred.

In addition, an ozone generator or an oxygen-containing gas supply means such as a diffuser may be provided in place of the chemical injection tank to supply ozone or oxygen to promote the generation of radicals.

When both the ultraviolet irradiation device 5 and the chemical injection tank are provided in the cavitation treatment liquid circulation line 4, the ultraviolet irradiation device 5 is provided in the first stage and the chemical injection tank is provided in the second stage. After that,
It is preferable that the oxidizing agent is added, and then the pressure is increased by the pressure pump 2 and the solution is sent to the cavitation generating means.

The processing solution thus decomposed is shown in FIGS.
Although not shown in FIG. 3, if necessary, an ion exchange resin, an ion exchange means such as an ion exchange membrane, a membrane separation means,
Processing may be performed by appropriately combining processing means such as degassing means.

Furthermore, it is possible and preferable to return the treatment liquid to the primary pure water system and reuse it as water for producing ultrapure water. As a result, the amount of water used can be significantly reduced.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to examples, but it is merely an example, and the present invention is not limited thereto.

(Example 1) IP in pure water as a TOC component
A solution to which A, DMSO and TMAH were added so that the total concentration became 1000 ppb was used as a liquid to be treated, and TOC decomposition treatment was performed using the apparatus shown in FIG. 1 under the following conditions. That is, the cavitation process is repeated 10 times,
Thereafter, an ultraviolet irradiation treatment was performed.・ Pump discharge pressure: 0.4MPa ・ Ultraviolet irradiation condition: Ultraviolet lamp wavelength 254nm (using high pressure UV oxidizer)

The TOC component in the processing solution after the decomposition treatment is converted to TO
C meter: SIEVERS-810 (SIEVERS In
(manufacturers, Inc.) was 100 ppb. The results are shown in Table 1.

Example 2 Using the same liquid to be treated as in Example 1, cavitation and ultraviolet irradiation were repeated 10 times using the apparatus shown in FIG.

The TOC component in the processing solution after the decomposition treatment was analyzed in the same manner as in Example 1, and it was found to be 100 ppb. The results are shown in Table 1.

Example 3 Using the same liquid to be treated as in Example 1, cavitation treatment and ultraviolet irradiation treatment were performed using the apparatus shown in FIG. 3 without performing circulation processing.

The TOC component in the treatment liquid after the decomposition treatment was analyzed in the same manner as in Example 1, and found to be 500 ppb. The results are shown in Table 1.

[0049]

[Table 1]

As is clear from Table 1, in Examples 1 and 2 in which the apparatus was provided with a circulation line, the TOC concentration in the processing solution could be reduced to 1/10 of that before the processing. Became clear. That is, by providing a circulation line in the apparatus and circulating and simultaneously performing an ultraviolet irradiation treatment, the TOC concentration in the treated water finally becomes 100 p.
It turned out to have decreased to pb.

On the other hand, it was also found that the TOC concentration was reduced by half as compared with the liquid to be treated also in Example 3 having no circulation line.

[0052]

From the above, it is apparent that TOC
By promoting the generation of OH radicals and performing cavitation treatment on the cleaning wastewater in the semiconductor manufacturing process containing the components, the TOC component can be decomposed in a lump and efficiently with low energy.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of one embodiment of the present invention.

FIG. 2 is a schematic diagram of another embodiment of the present invention.

FIG. 3 is a schematic diagram of another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 tank 2 pressure pump 3 cavitation nozzle 4 circulation line 5 ultraviolet irradiation device

Claims (5)

[Claims] 1. A processing apparatus for treating cleaning wastewater in a semiconductor manufacturing process, comprising: a liquid sending means for pressurizing and sending the cleaning wastewater; and a pressurized processing liquid pressurized and sent by the liquid sending means. Cavitation generating means for injecting and generating cavitation in the injected pressurized processing liquid, and at least one of before and after the cavitation generating means, and for promoting generation of OH radicals in the liquid to be processed. A wastewater treatment apparatus comprising at least one radical generation promoting means. 2. The wastewater treatment apparatus according to claim 1, further comprising a circulation unit that returns the cavitation treatment liquid discharged from the cavitation generation unit to an upstream side of the cavitation generation unit. 3. The wastewater treatment apparatus according to claim 1, wherein the pressure applied by the liquid sending means is 1 MPa or less. 4. A wastewater treatment apparatus according to claim 1, wherein said radical generation promoting means includes at least one of an ultraviolet irradiation device and an oxidizing agent adding device. . 5. A processing method for treating cleaning wastewater in a semiconductor manufacturing process, wherein the cleaning wastewater is pressurized and jetted to generate cavitation in a pressurized processing solution and to perform at least one of before and after the occurrence of the cavitation. A wastewater treatment method characterized by promoting the generation of OH radicals in a treatment liquid.