Inorganic impurity removal from waste oil and wash-down water by Acinetobacter johnsonii

► Process was developed to cleanse waste oil using Acinetobacter johnsonii. ► Inorganic impurity in waste oil was reduced below 0.5% after biotreatment. ► Turbidity and sulfides in wash-down water were controlled within 100 NTU and 1 mg/L. ► Inorganic impurity in oil phase was removed by wettability reversal. ► Inorganic impurity in water phase was removed by bioflocculation.