Patent ID: 7338605

Claim:
A method for removing metal particles, tramp oil, and other contaminants from an oil-in-water emulsion produced in a metal working process, the method comprising: supplying a filter aid comprised of a cellulosic material and a cationic polymer flocculating agent to the oil-in-water emulsion to form a mixture; allowing the filter aid to react with the oil-in-water emulsion for a predetermined amount of time in order to form a floc therein; passing a flow of the oil-in-water emulsion mixture through the filter aid and a filter sheet in order to filter the floc and other contaminants from the oil-in-water emulsion; collecting filtered oil-in-water emulsion from the filter aid; supplying an acid material to the mixture of the oil-in-water emulsion and the filter aid after a predetermined pressure drop is detected across the filter sheet; and supplying dilute sodium hydroxide solution to the filter aid formed on the filter sheet after the acid material is supplied.