To provide a method for efficiently reusing oily waste water for washing a mechanical oil such as a cutting oil sticking on the surface of a workpiece or as a combustion improver for a burner.
Oily waste water 1 dispersing an oil particle therein in a waste water tank 2 is sent to a floating oil-type oil-water separation device 4 by a waste water pump 3. The oil concentration of the oily waste water 1 is about 50-100ppm. The oil particle therein is partially agglomerated in the separation device 4 and the oily waste water having the oil concentration increased to 35-60wt.% floats and is separated. The floating and separated waste water 5 in a high concentration waste water tank 6 is sent to an ultrafiltration device 9 by a waste water pump 8 and the oil content in the waste water 5 is increased by an ultrafiltration by using the ultrafiltration device 9. The ultrafiltered and concentrated waste water is separated to two streams and the one having about 90% of total amount is returned to the high concentration waste water tank 6 and sent to the ultrafiltration device 9 again to increase the concentration of the oil to 70-90wt.% and the other having about 10% of total amount and 70-90wt.% concentration is used as a combustion improver for a burner 10. On the other hand, waste water with the oil concentration lowered to 3-10ppm by permeation through the ultrafiltration device 9 is used for roughly washing of a mechanical oil sticking to workpiece stuck.
HIRANO TAKASHI
DOUKU TAKESHI
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