Decontamination of petroleum sludges by hot water extraction

The process of hot water extraction of tar sand was modified and adapted for removal of heavy oil from bottom tank petroleum sludges, and was submitted to a laboratory feasibility study. This process can also be utilized to clean beach sands contaminated by accidental heavy oil spills. In the case of oil contaminated sands, a single stage extraction has yielded a 99% recovery of hydrocarbons and clean sands (containing less than 0.1% of hydrocarbons) which are thus safe to be returned to the environment. In the case of petroleum bottom tank sludge, it was necessary to proceed with a double stage extraction with the addition of a wetting agent. A dosage of a Na 2 Si O 3 aqueous solution of 1% by weight has proven efficient, allowing an 82% recovery of hydrocarbons, with only 0.5% of hydrocarbons content in the solid residues.