JPS60118283A - Treatment of organic solvent-containing waste water - Google Patents

Abstract

PURPOSE:To prevent the clogging of a reverse osmosis membrane caused by colloidal particles, by concentrating and filtering waste water containing an org. solvent used in washing a semiconductor substrate by a reverse osmosis membrane and filtering the filtrate by an ultrafiltration membrane while mixing the obtained filtrate with before filtration using the reverse osmosis membrane. CONSTITUTION:Waste water from a receiving tank 2 is filtered by a reverse osmosis membrane filter 4 and the filtrate sufficiently reduced in the content of impurities such as an org. solvent is sent to an org. substance decomposition tank 5 and receives the mixing of hydrogen peroxide and irradiation of ultraviolet rays to decompose residual impurities such as an org. solvent. Subsequently, the treated filtrate is sent to an activated carbon filter 6 to remove particles of decomposed org. substances and sent to an ion exchange resin filter 7 to remove ions. Because the waste water passed through the ion exchange resin filter 7 is recovered as high purity water containing almost no impurities, it is again returned to a washing process 1 and used as washing pure water.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field This invention relates to a method for treating wastewater containing organic solvents for treating and reusing wastewater containing organic solvents.

(b) Prior Art In manufacturing semiconductor devices, semiconductor substrates and the like are cleaned using organic solvents and then purified water. However, the waste water from cleaning with pure water contains a trace amount of organic solvents such as trichlene remaining on semiconductor substrates and the like during organic cleaning. Therefore, this wastewater has biochemical oxygen demand (BOD) and chemical oxygen demand (CO
D) becomes high and cannot be discharged as is, so treatment using an activated sludge method or the like is required.

fc1 Purpose of the Invention This invention was made in view of the above-mentioned circumstances, and is intended to treat wastewater containing organic solvents used for cleaning semiconductor substrates by using a reverse osmosis membrane (R10) and an ultrafiltration membrane (UF). Provides a method for treating wastewater containing organic solvents that does not require treating and discharging wastewater by separating pure water and organic solvents from wastewater, recovering and reusing the wastewater. The purpose is to

FD1 Structure and effect of the invention This invention, in the process of treating wastewater containing TA solvent, filters the wastewater with a reverse osmosis membrane, filters the liquid concentrated with the reverse osmosis membrane with an ultrafiltration membrane, and It is characterized in that the filtrate from the ultrafiltration membrane is returned and mixed with the waste water before being filtered by the reverse osmosis membrane.

In the method for treating wastewater containing organic solvents of the present invention configured as described above, the filtrate of the reverse osmosis membrane can be obtained in a state with sufficient amounts of impurities such as organic solvents, so that the filtrate can be simply treated. It is possible to recover high-purity pure water, and it is economical because wastewater can be reused without having to be discharged.Also, the liquid that is not filtered by the reverse osmosis membrane is returned to the wastewater and mixed. Then, it is sent to the reverse osmosis membrane again and circulated between these membranes.As a result, the concentration of the organic solvent dissolved in the circulating wastewater increases, causing emulsion and becoming colloidal particles, which are passed through the ultrafiltration membrane. Therefore, the organic solvent can also be recovered at a high concentration, so if it is dehydrated and used as fuel for boilers, etc., there will be no waste.

Furthermore, since the colloidal particles are removed by the ultrafiltration membrane, it is possible to prevent the reverse osmosis membrane from being clogged by the colloidal particles.

The tel embodiment drawing is a block diagram showing the steps of a method for treating organic solvent-containing wastewater, which is an embodiment of the present invention.

In the cleaning process 1 for semiconductor substrates, etc., using pure water and an organic solvent, organic cleaning with the organic solvent is first performed, and then cleaning with pure water is performed. The wastewater discharged from the cleaning step 1 and containing a small amount of impurities such as organic solvents is stored in a tank 2. The waste water drawn out from the tank 2 is pressurized by a pump 3, and sent to a reverse osmosis membrane filter 4 where it is filtered. The filtrate that has been filtered through the reverse osmosis membrane filter 4 and has been sufficiently reduced in impurities such as organic solvents is sent to the organic matter decomposition tank 5, where it is mixed with hydrogen peroxide (H2O2) and irradiated with ultraviolet (UV) light. , decomposes residual organic substances such as organic solvents. The wastewater treated in the organic matter decomposition tank 5 is then sent to an activated carbon filter 6, where decomposed organic matter and other impurity particles are removed. The waste water that has passed through the activated carbon filter 6 is further sent to an ion exchange resin filter 7 to remove ions. The waste water that has passed through the ion-exchange resin filter 7 is recovered as highly pure water containing almost no impurities, so it is returned to the cleaning step 1 and used as pure water for cleaning. In addition, if the purity of the water is not sufficient even after passing through the activated carbon filter 6 or the ion exchange resin filter 7, a higher stage treatment may be performed.
Or use it for other applications where the water does not need to be very pure. The concentrated liquid that is not filtered by the reverse osmosis membrane filter 4 and has an increased concentration of impurities such as organic solvents is sent to the ultrafiltration membrane filter 8. And this ultrafiltration membrane filter 8
The filtrate is returned to the waste water in the receiving tank 2 and mixed therewith.

Therefore, the liquid that has not been filtered by the reverse osmosis membrane filter 4 will be circulated between the receiving tank 2 and the reverse osmosis membrane filter 4. Then, the organic solvent that has entered the circulating wastewater increases in concentration, emulsifies, becomes colloidal particles, and is removed by the ultrafiltration membrane filter 8.

In this way, the highly concentrated organic solvent removed by the ultrafiltration membrane filter 8 is dehydrated by the water removal device 9 and recovered as fuel for boilers, etc. As explained above, this organic solvent-containing wastewater is The treatment method is reverse osmosis membrane filter 4
The filtrate of 5. By treating the water with the activated carbon filter 6 and the ion exchange resin filter 7, highly pure water can be recovered, so there is no need to discharge wastewater, which is economical. In addition, since the organic solvent can be removed by the ultrafiltration membrane filter 8,
It can be recovered as fuel for boilers, etc., eliminating waste.

[Brief explanation of drawings]

The drawings are process diagrams showing the steps of a method for treating wastewater containing organic solvents, which is an embodiment of the present invention. 4-Reverse osmosis membrane filter (reverse osmosis membrane) 8-Ultrafiltration membrane filter (ffl outer filtration membrane applicant
Kansai NEC Co., Ltd. Representative Patent Attorney Hisao Komori

Claims (1)

[Claims] (1) In the process of treating wastewater containing organic solvents,
The wastewater is filtered through a reverse osmosis membrane, the liquid concentrated by the reverse osmosis membrane is filtered through an ultrafiltration membrane, and the filtrate from the ultrafiltration membrane is returned to and mixed with the wastewater before being filtered through the reverse osmosis membrane. A method for treating wastewater containing organic solvents.