This thesis is concerned with the biodegradation of oily sludges typically found at refinery sites as waste residues from the refining of mineral oil. Currently these type of wastes represent significant environmental risk. Current technology that addresses containment during treatment to regulate the release of volatile organic carbons and reduction of the polynuclear aromatic hydrocarbons in the sludge, is incineration. Incineration is a costly option and this research has shown that the same treatment standards as incineration is achievable through bioreactor treatment with the correct process and reactor design.