Abstract: In a method for reprocessing aqueous, oily and greasy cleaning solutions by separating oil and grease out of the solution in an oil separator, a mixture of oil, grease and cleaning solution separated in the oil separator is subjected to vaporization for the purpose of thickening it, the hot water vapor thereby resulting is used to heat the oil separator and the condensed water resulting from the vapor is fed back to the cleaning solution for its regeneration. An apparatus for performing this method is characterized in that the oil separator is enclosed by an outer casing, in the bottom region of which the separated cleaning solution containing oil and grease is collected and vaporized, the hot vapor thereby resulting being utilized to heat the cleaning fluid in the oil separator. A condensate collecting tray is provided between the bottom region of the outer casing and a bottom wall of the oil separator and condensed water flows from this tray back into the cleaning solution.