JP3043199B2 - Method and apparatus for treating recovered water to obtain reused water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is generally applied to high-purity water (generally pure water or ultra-pure water) used for cleaning or the like in equipment of the semiconductor manufacturing industry or equipment of the chemical manufacturing industry. High-purity water called pure water), after its use, is an effective method for treating recovered water when it is used as reused water in attached facilities, or raw water used in the production of the high-purity water used in main facilities TECHNICAL FIELD The present invention relates to a method and an apparatus for treating recovered water which are effective when reused as wastewater.

[0002]

BACKGROUND OF THE INVENTION In recent years, the use of high-purity water, called pure water or ultrapure water, as a washing water has recently become widespread, as has recently been widely used in semiconductor manufacturing facilities and the like. Water quality standards that are being demanded as these high-purity waters are generally such that even in current industrial-scale production facilities, the content of impurities is below the ppm level. In the field where the improvement of the cost and the reduction of the product cost are strictly required, it has been demanded to use water which does not contain even a very small amount of impurities based on the level of several tens of ppb to several ppb. ing. For this reason, various proposals effective for producing high-purity water have been made.

[0003] In actual industrial production facilities requiring high-purity water as described above, water is also used for various purposes in equipment attached to the main facilities. For example, various boilers and heat exchangers are usually used as accessory equipment, and in actual industrial equipment, water is used for various other purposes.

[0004] By the way, high-purity water, such as pure water or ultrapure water, used in a main production line is compared with general industrial water or city water even after it is used for washing or the like. Since the water quality is often good, as water for the production of pure water or ultrapure water as described above or as water used in equipment that is industrially classified as an auxiliary equipment such as a heat exchanger, It is common practice to use used wastewater after reuse in the main production line of Japan as reused water. This is preferable from the viewpoint of reducing wastewater from industrial equipment as much as possible.Moreover, in industrial equipment using groundwater or the like as raw water, its use is often limited in quantity. Industrial facilities in such areas are strongly required to reuse wastewater.

However, since the water used for cleaning and the like naturally removes dust and the like adhering to the object to be cleaned, the water quality is lower than that of high-purity water before use.
If the water is to be reused as it is, its use is greatly restricted. Therefore, in order to reuse the recovered water, a certain process is generally performed conventionally.

As a conventional treatment for reusing such waste water of high-purity water, for example, as shown in FIG. 4, the recovered water is passed through an activated carbon tank 101 to adsorb and remove organic substances. Further, ionic components are removed by passing through a desalting tower device 102 filled with a strongly acidic cation exchange resin and a weakly basic anion exchange resin, whereby the total organic matter (TOC) is reduced to 1 ppm. In many cases, recovered water having a water quality of about 500 ppm of total cations is regenerated as recycled water of about 0.1 ppm by TOC and about 10 ppm of total cations.

[0007]

However, in the conventional treatment for producing such recycled water, for example, the treatment capacity is limited to at most SV 5 to 10 because an activated carbon tank is used. When applied to a manufacturing facility that uses pure water, there is a problem that it is inevitable to increase the size of a treated facility for recovered water.

[0008] In addition, in the case of using the water for use in a heat exchange device such as a cooling tower for the purpose of reuse water, an appropriate chemical is conventionally added to prevent scale adhesion. Trace inorganic fine particles contained in
In particular, since the colloidal silica component which has a great influence on the scale generation cannot be removed by the conventional processing apparatus shown in FIG. 4, a device capable of removing this has been desired.

The present inventor proposes the present invention in view of the above-mentioned situation, and one of the objects is to provide high-purity water after using it in equipment using high-purity water. The present invention provides a treatment method and apparatus suitable for treating and effectively using recycled water.

Another object of the present invention is to provide a method of using the above-mentioned recycled water as a supply water and a makeup water for a heat exchanger, a boiler, etc., to remove a colloidal silica component which causes scale adhesion to the recycled water. It is an object of the present invention to provide a processing method and an apparatus which can be removed from the wastewater.

Still another object of the present invention is to improve the water use rate and recovery / reuse rate in equipment using high-purity water to reduce running costs, effectively use resources, and reduce the influence on the surrounding environment. It is an object of the present invention to provide a processing method and apparatus capable of realizing the above.

Still another object of the present invention is to provide a processing method and apparatus effective when cleaning water discharged from a main line of a semiconductor manufacturing facility or the like is reused as raw water used for cleaning water in the main line. It is for the purpose of providing.

[0013]

Means for Solving the Problems To achieve the above object, the present inventor has proposed a treatment method for collecting and reusing used wastewater of high-purity water, and in particular, a method of treating wastewater contained in the collected water. Since the ionic silica component is one of the major causes of the scale, for example, a intensive study was made on a treatment method capable of removing as much as possible.

As such a method, conventionally, for example,
Proposal of forcibly oxidizing inorganic fine particles (colloidal substances) that cause evaporation residues in ultrapure water into oxidized solid fine particles by ozone ("A Mechanistic Study of Ozone-
Induced Particle Destabilization ", JOURNAL AWWA, 19
91), but in this method, the proportion of colloidal silica components that are made into fine particles is small.

However, the inventor of the present invention has found that when the recovered water is treated by a combination of forced oxidation and ultraviolet irradiation, ionization of colloidal silica, which has not been expected at all, occurs.

The present invention has been made based on this finding. One of the features of the present invention is to recover the used waste water of high-purity water used for cleaning semiconductors and the like, and to obtain molybdic acid contained in the recovered water. A method of treating recovered water to obtain reusable water in which a nonionic silica component that does not react with a reagent is ionized, and then the ionic silica component is removed by membrane removal with a reverse osmosis membrane device.

In the above, in order to ionize the nonionic silica component, a step of bringing ozone gas into contact with the recovered water as an oxidizing agent, and a step of irradiating the recovered water with ultraviolet rays,
It may be performed as a simultaneous or sequential step. When using ozone gas, its concentration is 0.5 ppm or more, preferably 1 ppm or more, and optimally 3 to 4 ppm. The ultraviolet irradiation has an emission wavelength of 170 to 400 nm and a light amount of 0.35 WH / l or more. , Preferably 0.
It is good to be 7 WH / l or more. The oxidizing agent can be injected directly into the pipe of the recovered water or the oxidizing agent can be injected into the storage tank of the recovered water, and the ultraviolet irradiation is not limited. An apparatus that accommodates a light-emitting lamp and allows the collected water to flow close to the periphery of the case can be preferably used.

The used waste water of high purity water used as raw water in the above configuration is not limited, but may be used washing water used in a plating step or a washing step of semiconductor or liquid crystal device manufacturing equipment, Alternatively, in the chemical manufacturing industry, for example, washing water for ampoules can be typically mentioned.

The recovered water as raw water that is treated and reused as recycled water according to the present invention is not particularly limited, but generally, the total amount of organic matter (TO
C) is about 1 ppm, total cation is 500 ppm
It is preferable that the water quality is of the order.

The fact that it does not react with molybdic acid reagent is described in JI
It means that it does not react with the reagent used in the measurement of the molybdic acid yellow absorbance method of SK0101.

In the above description, the reverse osmosis membrane device for removing the ionic silica component from the membrane is not necessarily determined uniformly by the performance of the membrane. According to the reverse osmosis membrane device shown in Examples described later, it is preferable to use a device capable of removing the ionic silica component with a high efficiency of 60% or more, preferably 80% or more. The reverse osmosis membrane device may be provided with one or two membrane modules.

The feature of the present invention as an apparatus for performing such a processing method is that high-purity water is applied to a semiconductor or liquid crystal device.
A water supply unit that collects waste water of high purity used in facilities used in a plating process or a cleaning process of manufacturing water and sends the waste water to a collected water treatment unit, and a collected water treatment unit that treats the collected collected water. Water distribution means for distributing the treated water that has passed through the recovered water treatment means as reused water to the downstream equipment, wherein the recovered water treatment means does not react with the molybdic acid reagent contained in the supplied collected water. An ionization treatment device for ionizing the acidic silica component, and a reverse osmosis membrane device installed at the subsequent stage of the ionization treatment device and capable of removing membranes of the ionic silica component in the recovered water, and the ionization treatment device includes: The present invention is configured to include an oxidizing agent injection means for injecting ozone gas into the recovered water and an ultraviolet irradiation means for irradiating the recovered water with ultraviolet light.

The water distribution means of this apparatus includes, for example, a supply water supply pipe to a heat exchanger such as a cooling tower provided as an auxiliary device in a semiconductor manufacturing facility, a supply water supply pipe for various miscellaneous waters, various boilers. Connected to a supply water supply pipe to the It can also be circulated and reused as part of raw water for a high-purity water producing apparatus such as ultrapure water in a semiconductor production facility.

In the treatment apparatus of the present invention, a reducing agent (sodium thiosulfate or sodium sulfite) may be provided between the ionization treatment apparatus and the reverse osmosis membrane apparatus by providing an activated carbon tank or a tank filled with a palladium catalyst, or by providing an intermediate storage tank. Etc.) to remove residual ozone.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Embodiment 1 FIG. 1 is a diagram showing an example of the apparatus according to the present invention,
For example, used cleaning water after use of ultrapure water (not shown) for cleaning semiconductors and the like is collected, collected, and sent to the ionization apparatus 1 via the water pipe 3.

In the present embodiment, a measuring device 4 is provided in the middle of the path of the water supply pipe 3 to measure, for example, the conductivity and the TOC concentration of the recovered water, and when these values are below a predetermined reference value. Is sent to the above-mentioned ionization treatment apparatus 1, but when it exceeds the reference value, it is provided so as to switch the opening and closing of the switching valves 5 and 6 so that the water is directly discharged as unsuitable water for reuse. Such a configuration is not essential.

The ionization apparatus 1 in this embodiment is
While flowing the collected water from the lower part of the ozone diffusion tank 11 to the upper part, ozone gas is injected from the lower part of the tank 11 to oxidize the collected water. Next, the collected water flowing out from the upper part of the ozone diffuser tank 11 is irradiated with ultraviolet rays by an ultraviolet light emitting lamp incorporated in a transparent glass tube 13 while flowing from the lower part to the upper part of the ultraviolet irradiation device 12. . As described above, the nonionic silica component contained in the recovered water is ionized, and the organic matter contained in the recovered water is also decomposed.

The recovered water that has exited the ionization treatment apparatus 1 is then supplied to a reverse osmosis membrane apparatus 2, and the treated water that has passed through the membrane is reused as, for example, a cooling tower 20 shown in FIG.
Is supplied to the supply water pipe as supply water.

The cooling tower 20 shown in FIG. 2 is a well-known cooling tower which cools the medium in the piping system 22 appropriately by cooling water circulating between the cooling tower 20 and the cooling tower. Since scale adheres to the bottom portion 23, the inside of the pipe 24, or the pipe of the heat exchanger, a scale inhibitor or the like is usually injected with a chemical to prevent the scale. When replenishing the water for use, the amount of silica component in the water is extremely small, so that the adhesion of the scale is reduced even when the water is used, and the amount of the chemical can be greatly reduced even when the chemical is injected.

Embodiment 2 FIG. 3 shows an example in which the apparatus of FIG. 1 is applied to a washing water recovery system of a semiconductor manufacturing facility having an ultrapure water manufacturing apparatus. After producing ultrapure water through the secondary system pure water device 31 and the secondary system pure water device 33 through the circulation tank 32 in order, and using it for semiconductor cleaning at the point of use (UP), Then, the water is collected and sent to the ionization apparatus 1 through the water pipe 34 to ionize the non-ionic silica component by ozone diffusion and ultraviolet irradiation, and then the membrane is eliminated by the reverse osmosis membrane apparatus 2 to remove the treated water ( (Recycled water).

The obtained treated water can be used as make-up water or the like in the apparatus shown in FIG. 2, but since the quality of the water is high, the primary system pure water apparatus 31 or the secondary system pure water is used. It is circulated back to the pure water production line for use as raw water for the equipment . For example, it can be returned to a position on the inlet side of a mixed-bed polisher used as a substantially final treatment step of the primary system pure water apparatus.

Test Example Using the apparatus shown in FIG. 1, treatment of recovered water was performed under the following conditions. Injection ozone concentration ··· 104 g / Nm ³ Ozone injection amount ··· 4 liters / mi
n Ozone concentration in sample water: 2.5 to 3 ppm As sample water, concentrated wastewater (renewed chemical solution) used in the semiconductor manufacturing process was used. SU710 as reverse osmosis membrane
(Manufactured by Toray Industries, Inc.). The total silica component was measured using an inductively coupled plasma mass spectrometer ICP-MS (manufactured by Yokogawa Electric Corporation), and the ionic silica component was measured using a silica meter SA-
500 (manufactured by Toray Industries, Inc.).

For comparison, the silica component in the case where only the ozone diffusion was performed and the ultraviolet irradiation was not performed, the case where only the ultraviolet irradiation was performed and the ozone diffusion was not performed, and the case where no treatment was performed was performed. Was measured in each case .

[0034] 500pp As a result, present in the sample water
nonionic silica b is an ozone diffuser only, UV irradiation only, no change for an untreated, and when treated reverse osmosis membrane, a non-ionic silica 300ppb leaks.

On the other hand, in the present invention, nonionic silica is reduced to 20 ppb by ozone diffusion and ultraviolet irradiation treatment, and nonionic silica is reduced to 10 ppb by reverse osmosis membrane treatment. It can be seen that non-ionic silica can significantly reduce the treated water.
Was .

[0036]

According to the present invention, used high-purity water can be treated and effectively used as reused water, so that the water use rate and the recovery and reuse rate are improved, and the water is reused. There is an effect that scale adhesion on a heat exchanger, a boiler, or the like is effectively suppressed or reduced. Therefore, it is possible to reduce the chemical injection amount of the scale inhibitor conventionally used in the heat exchanger and the like, and to obtain effects such as a reduction in running cost.

Further, if the washing wastewater discharged from the main line of a semiconductor manufacturing facility or the like is reused as raw water used for the washing water of the main line, the water use efficiency is improved and the amount of wastewater from the facility is reduced. There is also an effect that can be done.

According to the recovered water treatment apparatus of the present invention,
As compared with the conventional apparatus, the processing speed can be increased, and therefore, there is also an effect that the installation area per unit processing amount can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a recovered water treatment apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a case where reused water treated by the apparatus shown in FIG. 1 is used as makeup water for a cooling tower.

FIG. 3 is a diagram showing an outline of a configuration of equipment provided to treat recovered water from an ultrapure water production apparatus.

FIG. 4 is a diagram showing an example of a conventional apparatus for treating recovered water as reused water.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ionization apparatus, 2 ... Reverse osmosis membrane apparatus, 1
1 ... Ozone diffuser tank, 12 ... Ultraviolet irradiation device.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-188988 (JP, A) JP-A-2-227185 (JP, A) JP-A 5-96277 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C02F 1/44 C02F 1/32 C02F 1/58 C02F 1/78

Claims (3)

(57) [Claims] 1. Plating of semiconductor and liquid crystal device manufacturing equipment
The used wastewater of the high-purity water used in the process or the washing process is collected, and the nonionic silica component which does not react with the molybdic acid reagent contained in the collected water is converted into ozone gas by the collected water.
Contacting with water and irradiating recovered water with ultraviolet light
A method for treating recovered water for obtaining reused water, characterized by further ionizing and then removing the ionic silica component by membrane exclusion with a reverse osmosis membrane device. 2. High-purity water is used for manufacturing semiconductors and liquid crystal devices.
A water supply means for collecting used high-purity water discharged from equipment used in a plating step or a washing step and sending it to a collected water treatment means, a collected water treatment means for treating the supplied collected water, and the collection A water distribution means for distributing the treated water that has passed through the water treatment means as reused water to a downstream facility, wherein the recovered water treatment means is a nonionic silica that does not react with the molybdic acid reagent contained in the recovered water sent. An ionization treatment device for ionizing the components, and a reverse osmosis membrane device which is installed at the subsequent stage of the ionization treatment device and has a membrane elimination capability of the ionic silica component in the collected water, and the ionization treatment device is provided for the collected water. Oxidant injection means for injecting an oxidant,
And an ultraviolet irradiation means for irradiating the recovered water with ultraviolet light. 3. An apparatus according to claim 2, wherein the oxidizing agent injected into the recovered water by the oxidizing agent injection means is ozone gas.