JPH04354583A - Waste water treatment and apparatus thereof - Google Patents

Abstract

PURPOSE:To decrease the total org. carbon-content in raw water so as to stabilize the performance of a reverse osmosis membrane and to make the thickening operation by a membrane over a long period of time as well as to decrease the amt. of the waste water to be ejected to the outside of a system by thickening of the waste water by interposing a membrane treating stage using an oil-water separating semipermeable membrane having water selective permeability as a pretreatment with the reverse osmosis membrane. CONSTITUTION:The waste water of the water washing from a system for washing away the solder flux residue of a packaged printed circuit board by a detergent substitutive for fluorocarbon is first pretreated with the oil-water separating semipermeable membrane 6 having the water selective permeability and is then subjected to the thickening treatment with the reverse osmosis membrane 11. Namely, the membrane treating process by the oil- water separating semipermeable membrane having the water selective permeability is interposed as the pretreatment of the reverse osmosis membrane, by which the total org. carbon- content in the raw water can be decreased by about 30%. The performance of the reverse osmosis membrane is extremely stabilized in this way and the thickening operation by the membrane over a long period of time is executed. In addition, the amt. of the waste water to be ejected to the outside by the thickening of the waste water can be decreased. Further, the waster is saved by recycling of the waste water.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a wastewater treatment method and a wastewater treatment device in a cleaning system using a cleaning agent replacing fluorocarbons, and more particularly, the present invention relates to a wastewater treatment method and a wastewater treatment device for a cleaning system using a cleaning agent replacing fluorocarbons. The present invention relates to a wastewater treatment method and a wastewater treatment apparatus using a membrane for water washing wastewater discharged from a process of washing and removing it with a detergent substitute for fluorocarbons.

0002

2. Description of the Related Art Conventionally, fluorocarbon-based cleaning agents have been used to clean and remove residual rosin-based solder flux after electronic components are mounted on printed wiring boards by soldering. There is a need for alternatives to fluorocarbon-based cleaning agents due to environmental concerns, and one idea is to use a combination of surfactants and non-halogen oil-based solvents such as terpene-based, petroleum-based hydrocarbons, and higher alcohol-based solvents that dissolve rosin. A CFC alternative cleaning agent is being considered, but if this cleaning agent is used, it is expected that a large amount of wastewater will be discharged from the cleaning process, which will cause problems in wastewater treatment.

As a method for concentrating an aqueous surfactant solution using a reverse osmosis membrane, for example, a method using a polyamide membrane as disclosed in Japanese Patent Application Laid-Open No. 179188/1984 is known. The processing is described in, for example, Japanese Patent Laid-Open No. 118283/1983.

0004

[Problems to be Solved by the Invention] The system for cleaning and removing solder flux residue from mounted printed wiring boards using the above-mentioned fluorocarbon alternative cleaning agent consists of approximately three steps, which are performed in this order: a cleaning process using a fluorocarbon alternative cleaning agent, a water washing process, and a drying process. Become.

[0005] The present inventor relates to a method of concentrating wastewater from the water washing process in this washing system using a membrane, and furthermore, a method of using various membranes, particularly a reverse osmosis membrane, in order to reuse the waste water. After investigation, it was found that when the membrane was used alone, the permeation flux rapidly decreased and it could not withstand long-term operation.

Therefore, the object of the present invention is to provide a method for stably and continuously concentrating a large amount of water washing wastewater from a washing process using a surfactant-containing fluorocarbon substitute detergent by a membrane separation method; Our goal is to provide that device.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on pre-treatment for concentration treatment using a reverse osmosis membrane, and have found that pre-treatment using a specific membrane is promising. Based on this knowledge, the present invention was completed.

That is, the present invention provides a cleaning system for cleaning and removing solder flux residue from a mounted printed wiring board using a surfactant-containing fluorocarbon alternative cleaning agent, from the water washing step performed after cleaning with the fluorocarbon alternative cleaning agent. Provided is a wastewater treatment method in a fluorocarbon alternative cleaning agent cleaning system, characterized in that when wastewater is concentrated using a reverse osmosis membrane, a step of treating it with an oil-water separation semi-permeable membrane having water selective permeability is inserted before the concentration treatment. Further, the present invention provides water cleaning performed after cleaning with a fluorocarbon alternative cleaning agent in a cleaning system that uses a surfactant-containing fluorocarbon alternative cleaning agent to remove solder flux residue from a mounted printed wiring board. This is a device that treats wastewater from a process, and incorporates a multi-stage membrane treatment process of treating it with a water-selective oil-water separation semipermeable membrane and concentrating this permeated water with a reverse osmosis membrane. The present invention provides a wastewater treatment device in a fluorocarbon alternative cleaning agent cleaning system.

The reverse osmosis membrane used in the present invention may be any commonly used reverse osmosis membrane, but cross-linked polyamide composite membranes are preferably used, and the type of membrane module is not particularly limited. Various types can be used, such as flat plate type, cylindrical type, spiral type, and hollow fiber type.

[0010] Furthermore, the water selectively permeable oil/water separation semipermeable membrane according to the present invention refers to a hydrophilic semipermeable membrane that selectively allows water to pass through while hardly allowing oily substances to pass through, and has a magnification of 10,000 times. It is preferable that no pores be found in the active layer of the membrane when observed under an electron microscope, and that the membrane is made of a membrane material having hydroxyl groups. Particularly preferred membrane materials include β-polyglucose, which is formed by bonding glucose through β-glucoside bonds. Similar to the reverse osmosis membrane, the type of module using the above membrane is not particularly limited, and the various types described above can be used. An example of such a water-selective oil/water separation semipermeable membrane module is a β-polyglucose hollow fiber semipermeable membrane module available from SDI (Separation Dynamics, Inc.).

[0011] Preferred TOC of wastewater that can be treated according to the present invention
The (total organic carbon) concentration is 1000 mg/liter or less, and if the TOC concentration exceeds 1000 mg/liter, it is desirable to perform oil-water separation pretreatment such as coalescer method or coagulation precipitation method.

Furthermore, in the present invention, purified water obtained by treatment with a reverse osmosis membrane can be used as is or by being treated with ion exchange and/or activated carbon, so that all or part of the water can be treated with a fluorocarbon substitute cleaning agent. It can also be reused by returning it to the water washing step performed after washing.

[0013]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

Example 1 A schematic diagram illustrating an example of the wastewater treatment method according to the present invention is shown in FIG. The present embodiment will be described below based on FIG.

In the water cleaning process, the cleaning liquid remaining on the mounted printed wiring board after cleaning with a fluorocarbon substitute cleaning agent is washed away with water. After passing through the filter 5, it is sent to a pretreatment semipermeable membrane (water selectively permeable oil/water separation semipermeable membrane) module 6 for pretreatment. This permeated water is stored in an intermediate tank 8 through an outlet line 7. On the other hand, the concentrated water is returned to the first washing tank 1 through the circulation line 9.

The permeated water stored in the intermediate tank 8 is pumped by a pressure pump 10 to a reverse osmosis membrane module 11 for treatment. The purified water obtained by permeating through the reverse osmosis membrane passes through the return line 12, either as it is or after being treated with an ion exchange resin and/or activated carbon treatment device 13, and then sent to the third washing tank 3 for reuse.

The washing waste water from the second washing tank 2 is finally concentrated in the first washing tank 1. Further, the concentrated water is returned to the first washing tank 1 through the circulation line 14 and reused.

As a fluorocarbon alternative cleaning agent, Cold Cleaner 375 (trade name, manufactured by Henkel Hakusuisha Co., Ltd.), which consists of a petroleum-based hydrocarbon solvent and an aliphatic polyether-based nonionic surfactant, was used.

The semipermeable membrane module 6 has a membrane area of 4 m.
2 Extran hollow fiber membrane (β-polyglucose membrane) module manufactured by SDI was used. As the prefilter 5, a precision filtration membrane with a pore size of 20 μm was used.

The reverse osmosis membrane module 11 is a crosslinked polyamide composite membrane spiral type module SV-02 manufactured by Daicel Chemical Industries, Ltd. with a membrane area of 1.1 m2.
2-DRA-98 was used.

[0021] TOC concentration of washing wastewater from second washing tank 2: 20
The value of mg/liter becomes 118 mg/liter, which is about 10 times due to the concentration reaching the circulation line 9 of the pretreatment semipermeable membrane module 6, and further increases to 118 mg/liter in the circulation line 1 of the reverse osmosis membrane module 11.
Concentration up to step 4 resulted in an approximately double concentration of 391 mg/liter, resulting in a total concentration of approximately 20 times. Moreover, the TOC concentration of purified water obtained by the treatment of the reverse osmosis membrane module 11 was 5 mg/liter.

Example 2 Instead of the second washing tank cleaning wastewater used in Example 1, TO
Washing wastewater (raw water) with a C concentration of 434 mg/liter was used for membrane treatment in the same modules as in Example 1 according to the schematic flow shown in FIG. 2. Note that the symbols in FIG. 2 are the same as in FIG. 1.

The TOC concentration of the permeated water obtained by treatment with the pretreatment semipermeable membrane module 6 was 285 mg/liter,
The TOC removal rate was 34%, and the TOC concentration of purified water obtained by treatment with the reverse osmosis membrane module 11 was 6 m
g/liter, TOC removal rate by two-stage membrane treatment is 98
%. The change over time in the permeation flux of the reverse osmosis membrane according to this example is shown in FIG. 3 by circles. From FIG. 3, it can be seen that the performance of the reverse osmosis membrane is extremely stable by intervening pretreatment using a water-selective oil-water separation semipermeable membrane module before the reverse osmosis membrane treatment.

Comparative Example In Example 2, membrane treatment was performed using only a reverse osmosis membrane without using a pretreatment semipermeable membrane. The results are shown as ● in FIG. From FIG. 3, it can be seen that in membrane treatment using only a reverse osmosis membrane, the permeation flux quickly becomes almost zero.

[0025]

Effect of the invention: By interposing a membrane treatment process using a water-selective oil-water separation semipermeable membrane as a pretreatment for reverse osmosis membranes, the TOC component in raw water can be reduced by about 30%. The performance of the reverse osmosis membrane is extremely stable, enabling long-term concentration operation using the membrane, and by concentrating wastewater, the amount of wastewater discharged from the system can be reduced. Also,
Water can be saved by reusing wastewater.

[Brief explanation of drawings]

FIG. 1 is a schematic flow diagram illustrating an embodiment of the wastewater treatment method of the present invention.

FIG. 2 is a schematic flow diagram for explaining a second embodiment.

FIG. 3 is a diagram showing changes over time in permeation flux obtained in Example 2 and Comparative Example.

[Explanation of symbols]

1 First washing tank 2 Second washing tank 3 Third washing tank 4 Liquid pump 5 Pre-filter 6 Pretreatment semipermeable membrane module 7 Outlet line 8 Intermediate tank 9 Circulation line 10 Pressure pump 11 Reverse osmosis membrane module 12 Return line 13 Ion exchange resin and/or activated carbon treatment device 14 Circulation line

Claims (6)

[Claims] Claim 1: A cleaning system for cleaning and removing solder flux residue from a mounted printed wiring board using a fluorocarbon alternative cleaning agent containing a surfactant, in which waste water from a water cleaning process performed after cleaning with the fluorocarbon alternative cleaning agent is provided. , A wastewater treatment method in a fluorocarbon alternative cleaning agent cleaning system, characterized by interposing a step of treatment with an oil/water separation semipermeable membrane having water selective permeability prior to concentration treatment with a reverse osmosis membrane. 2. In a cleaning system that uses a surfactant-containing fluorocarbon alternative cleaning agent to remove solder flux residue from a mounted printed wiring board, waste water from a water cleaning process performed after cleaning with the fluorocarbon alternative cleaning agent is provided. The treatment apparatus is characterized by incorporating a multi-stage membrane treatment process including a process using a water-selective oil-water separation semipermeable membrane and a process of concentrating the permeated water using a reverse osmosis membrane. Wastewater treatment equipment in a cleaning system using a fluorocarbon alternative cleaning agent. Claim 3: Purified water or concentrated water obtained by treatment with a reverse osmosis membrane can be used as is, or can be treated with ion exchange and/or activated carbon to replace all or part of it with fluorocarbons. The wastewater treatment method according to claim 1, wherein the wastewater treatment method is recycled by returning it to a water washing step performed after washing with a detergent. 4. The oil/water separation semipermeable membrane having water selective permselectivity is characterized in that it is a β-polyglucose hollow fiber type semipermeable membrane in which pores cannot be substantially confirmed by electron microscopic observation at a magnification of 10,000 times. The wastewater treatment method according to claim 1. 5. The water-selective oil-water separation semipermeable membrane is characterized in that it is a β-polyglucose hollow fiber type semipermeable membrane in which substantially no pores can be observed by electron microscopic observation at a magnification of 10,000 times. The wastewater treatment device according to claim 2. 6. The wastewater treatment method according to claim 1, wherein the TOC (total organic carbon) concentration of the wastewater from the water washing step in which the membrane treatment is performed is 1000 mg/liter or less.