The batch bioreactor with a maximum capacity of 0.28 $m^3$ was designed and manufactured according to oilfield conditions Acinetobacter johnsonii ioslated from waste oil in an aerobic environment was employed to cleanse waste oil and wash-down water using the bioreactor in a pilot scale. The aerating process was optimized from 2 to 4 $m^3$/h corresponding to the different cell growth phases, ensuring sufficient dissolved oxygen and avoiding cell damage from the shearing forces due to strong aeration. The bio-treatment of waste oil underwent two stages:one was the wettability reversal of inorganic admixtures from oil phase into waster phase through enlarged wetting angles, and the other was the bio-flocculation in waster phase by intermediate metabolites excreted by cells. Finally, inorganic admixtures were effectively removed from waste oil and wash-down water at the optimal conditions, with the content less than 0.5% in oil phase and turbidity and sulfide less than 100 NTU and 1 mg/L in the water phase, respectively. Such bio-treatment made the oil-water interface clear against oil and water emulsification and in favor of smooth reclamations for waste oil and wash-down water.