JP3004432B2 - Wastewater treatment method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating wastewater, and more particularly to a method and an apparatus for treating emulsion wastewater.

[0002]

2. Description of the Related Art Treating waste water in an emulsion state to separate it into oil and water is an important but difficult technique in waste water treatment. There have been proposed various techniques for breaking an emulsion of an oil-water mixture in an emulsion state and separating oil-water. Of these,
As a device using a separation membrane, for example, JP-A-61-2
No. 54208 discloses a technique in which an emulsion waste oil is pretreated and then treated with an ultrafiltration membrane.
Japanese Patent Publication No. 57-42 discloses a technology for concentrating and separating a waste cooling body stream containing an oil-in-water emulsion using a semipermeable membrane.
No. 120 discloses a technique for concentrating an oil-in-water emulsion with a semi-permeable membrane, and Japanese Patent Publication No. Sho 60-2117 discloses a technique for concentrating an emulsion of an alkaline solution discharged from a vegetable oil / fat refining process with a semi-permeable membrane. However, JP-A-62-33589 proposes a technique for concentrating oil-containing wastewater containing a surfactant using an ultrafiltration membrane.

[0003] By the way, in order to clean rosin-based solder flux remaining after an electronic component is mounted on a printed wiring board by soldering, a CFC-based cleaning agent has been conventionally used. However, there is a need for alternative detergents due to environmental issues, and a CFC alternative detergent consisting of a combination of a non-halogen oil solvent such as terpene hydrocarbon, petroleum hydrocarbon and higher alcohol that dissolves rosin and a surfactant has been developed. Are being considered.

[0004]

When the above-mentioned CFC substitute detergent is used, a large amount of emulsion wastewater is discharged from the washing step, and a wastewater treatment technique for efficiently treating this wastewater is required. .

[0005]

Means for Solving the Problems As a result of intensive studies on a method for treating emulsion waste water, the present inventors have found that by performing a specific treatment operation using a specific membrane, the emulsion is rapidly destroyed, and oil separation is prevented. The inventor has found that it can be done very easily and completed the present invention.

That is, the first aspect of the present invention is that the emulsion wastewater has at least two-stage water-permeability and oil-water separation properties.
A wastewater treatment method characterized by separating the oil layer by allowing the concentrated liquid to stand by separating the oil layer by allowing the concentrated liquid to stand by separating the oil layer by subjecting the concentrated liquid to a concentrated treatment with a hydrophilic semipermeable membrane and breaking the emulsion to facilitate oil-water separation. The second is an emulsion wastewater treatment device, which is composed of at least two stages of water-permeability and oil-water.
A wastewater treatment apparatus comprising: a concentration treatment step of concentrating the emulsion using a hydrophilic semipermeable membrane having separability until an emulsion is broken; and a step of separating an oil layer from a concentrated liquid by a decanter. That is, in the first aspect of the present invention, the emulsion wastewater is concentrated by at least two-stage water-selective oil-water separation semipermeable membrane, and the emulsion is broken to facilitate oil-water separation. Is a wastewater treatment method characterized by separating the oil layer by allowing the oily water separation semi-permeable membrane of the second aspect of the present invention is an emulsion wastewater treatment apparatus, comprising at least two-stage water-selective oil-water separation semipermeable membrane. A wastewater treatment apparatus, comprising: a concentration treatment step of concentrating until emulsion breakage occurs; and a step of separating an oil layer from a concentrate by a decanter.

The wastewater treated in the present invention includes:
It is in an emulsion state. Such wastewater is not particularly limited, but is preferably applied to wastewater from a water washing step performed after washing and removing a solder flux residue of a mounted printed wiring board using a surfactant-containing Freon substitute detergent. As a system for cleaning and removing the solder flux residue of the mounted printed wiring board using a CFC substitute cleaning agent, a cleaning process using a CFC substitute cleaning agent,
It comprises a water washing step and a drying step. Emulsion wastewater that is preferably treated in the present invention is wastewater from the water washing step in the washing system as described above. The preferred TOC (total organic carbon) concentration of the wastewater that can be treated according to the present invention is 1000 mg / liter or less, particularly 500 mg / liter or less. Further, the emulsion type is preferably O / W.

[0008] The water permselective and oily water used in the present invention
The hydrophilic semi-permeable membrane having releasability is a hydrophilic semi-permeable membrane that allows water to permeate selectively without transmitting any oily substance,
No pores can be substantially confirmed in the active layer of the film even by observation with an electron microscope at a magnification of 10,000 times, and a film material having a hydroxyl group is preferable. As a membrane material,
Cellulosics such as regenerated cellulose and saponified cellulose acetate are preferable, and β-polyglucose in which glucose is bound by β-glucosidic bond can be exemplified as particularly preferable. Further, the film may be a composite film as long as the active layer is a cellulose-based film. The type of the module using the membrane is not particularly limited, and various types such as a flat plate type, a cylindrical type, a spiral type, and a hollow fiber type can be used. Among these, a hollow fiber type is preferable, and particularly a cellulose-based hollow fiber having an inner diameter of 300 to 1000 μm, an outer shape of 500 to 1500 μm,
It is preferable to use a compound having a molecular weight cut-off of 20,000 to 100,000 and to perform internal pressure treatment by a cross-flow method in which the circulation flow rate is 1/5 to 1/10 that of a normal ultrafiltration membrane.

[0009] In the present invention, the above water permselective
At least two stages of concentration treatment using a hydrophilic semipermeable membrane having oil-water separation properties are performed. This makes it possible to efficiently concentrate the emulsion wastewater with less clogging than in the case where only one stage is used, and furthermore, the emulsion is destroyed, and the separation of the oil component by the subsequent decanter is facilitated.
The standing of the concentrated liquid does not mean that the liquid is completely retained, and may be a normal decanter treatment.

[0010]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Embodiment 1) According to the process diagram shown in FIG. 1, wastewater from a water washing step performed after washing and removing a solder flux residue from a mounted printed wiring board using a CFC substitute cleaning agent was treated. In FIG. 1, a mounted printed wiring board (not shown) washed with a CFC substitute cleaning agent is washed in the order of a first washing tank 1, a second washing tank 2, and a third washing tank 3 as a washing step. Further, pure water 18 is supplied to the third washing tank 3,
The washing water overflowing from the third washing tank 3 flows to the first washing tank 1 sequentially. Therefore, the first washing tank 1 has the highest concentration of the CFC substitute cleaning agent and is in an emulsion state. The washing wastewater stored in the first washing tank 1 is sent to the raw water tank 4 and then the raw water pump 5
, A first-stage concentration treatment is performed in the first membrane separation device 7 through the pre-filter 6. The concentrated water 8 is sent to an intermediate tank 10, while the permeated water 9 is discharged to a sewer or the like.

The water stored in the intermediate tank 10 is sent to the second membrane separation device 12 by the intermediate pump 11. Here, the permeated water 14 is returned to the raw water tank 4, and the concentrated water 13 is sent to the decanter 15, where it is separated into an emulsion layer 17 and an oil layer 16. The oil layer 16 is carried out of the system, while the emulsion layer 17 is returned to the raw water tank 4 and processed again.

The first membrane separator 7 used three hollow fiber modules having a membrane area of 30 m ² , and the second membrane separator 12 used two hollow fiber modules having a membrane area of 4 m ² . Each module is made of a cellulosic material and has an inner diameter of 4
It is a hollow fiber having a diameter of 00 μm, an outer diameter of 650 μm, and a molecular weight cut off of 60,000.
Using the thing of 65 degreeC, it processed by the internal pressure cross flow method. The prefilter 6 has a pore size of 10 μm.
Was used.

TO in the waste water of the first washing tank 1 to be treated
The C concentration was 1000 mg / liter, and the flow rate was 1 m ³ /
H and sent to raw water tank 4. As a result, in the steady state, the flow rate of the concentrated water 8 by the first membrane separation device 7 was 20 L / H, the TOC concentration was 30,000 mg / L , and the TOC concentration of the permeated water 9 was 400 mg / L. The concentrated water 1 further concentrated in the second membrane separation device 12
3 has a flow rate of 2 liters / H and a TOC concentration of 300,00
The concentration was 0 mg / liter, and the concentration was 300 times as a whole. In the concentrated water 13 of the second membrane separation device 12, the emulsion was partially destroyed due to the high concentration of the detergent, and the decanter 15 could easily separate the emulsion into an oil layer and an emulsion. The oil layer 16 separated by the decanter 15 was carried out of the system at a flow rate of 1 liter / H, and the emulsion layer 17 was returned to the raw water tank at a flow rate of 1 liter / H.

[0015]

EFFECT OF THE INVENTION By using the wastewater treatment method or treatment apparatus of the present invention, emulsion-type wastewater which has been difficult to concentrate and separate in the past, especially solder flux residue of a mounted printed wiring board, is replaced with a surfactant-containing cleaning agent containing a surfactant. It is possible to easily treat the wastewater from the water washing step performed after the washing and removal by using.

[Brief description of the drawings]

FIG. 1 is an example of a wastewater treatment step that can be employed in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 First washing tank 2 Second washing tank 3 Third washing tank 4 Raw water tank 6 Prefilter 7 First membrane separation device 12 Second membrane separation device 15 Decanter 16 Oil layer 17 Emulsion layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI B01D 63/02 B01D 63/02 71/12 71/12 C02F 1/44 C02F 1/44 F (58) Fields surveyed (Int. Cl. ⁷ , DB name) B01D 17/00-17/12 B01D 61/14 B01D 61/58 B01D 63/02 B01D 71/12 C02F 1/44

Claims (6)

(57) [Claims] 1. An emulsion wastewater is concentrated by a hydrophilic semipermeable membrane having at least two stages of water-selective permeability and oil-water separation, and the emulsion is broken to facilitate oil-water separation. A wastewater treatment method characterized by separating an oil layer by allowing to stand still. 2. The waste water from the water washing step which is performed after washing and removing the solder flux residue of the mounted printed wiring board by using a surfactant-containing Freon substitute detergent. Item 4. The wastewater treatment method according to Item 1. 3. A hydrophilic material having water- permeability and oil-water separation properties.
Sex semipermeable membrane is, magnification 10,000 times substantially claim 1 or claim 2 wastewater treatment method wherein a hole is cellulosic hollow fiber semipermeable membrane which can not be confirmed by electron microscopy. 4. An apparatus for treating an emulsion wastewater, comprising at least two stages of water permselectivity and oil / water separation.
A wastewater treatment apparatus, comprising: a concentration treatment step of concentrating the emulsion by the use of a hydrophilic semipermeable membrane having the above, until the emulsion is broken; and a step of separating an oil layer from the concentrate by a decanter. 5. The emulsion waste water is a waste water from a water washing step performed after washing and removing a solder flux residue of a mounted printed wiring board using a surfactant-containing Freon substitute detergent. Item 5. A wastewater treatment device according to Item 4. 6. A hydrophilic material having water- permeability and oil-water separation properties.
Sex semipermeable membrane is, magnification 10,000 times wastewater treatment apparatus substantially holes, characterized in that it is a cellulose-based hollow fiber semipermeable membrane can not be confirmed according to claim 4 or claim 5, wherein the electron microscopy.