Bioremediation and immobilisation of oily sands containing naturally occurring radioactive material (NORM)

Abstract

The precipitation of radioactive substances from produced formation water during the production of oil and gas causes the accumulation of naturally occurring radioactive materials (NORM) in processing equipment. The resulting oily sandy waste stream has a level of radioactivity and contains volatile organic compounds, heavy metals and other petroleum hydrocarbon based contamination. This poses a potential health, safety and environmental risk. Treatment mechanisms for such waste must therefore address both radioactive and hydrocarbon contamination. This paper focuses primarily on the hydrocarbon contamination, and considers bioremediation and immobilisation as treatment mechanisms. Bioremediation of the oily fraction of this waste is examined using four different types of bacteria: Aspergillus niger, Acinetobacter calcosleticus, Pseudomonas aerogenousa and Rhodococcus ruber as possible additives. The use of naturally acclimated organisms generated in bioremediation of oily industrial residues is also examined. Immobilisation treatment with the purpose of capturing the oily fraction of the waste was also evaluated by limiting bioavailability though micro- and macro-encapsulation of the organic components of the waste. Leachability subsequent to immobilisation was assessed to determine the suitability of the treatment for long-term encapsulation and containment. The results in this paper demonstrated how treatment by immobilisation (also referred to as solidification or stabilisation) proved to be the most successful approach with leachate results validating effective binding of the hydrocarbon component.