Bacterial liberation of crude oil from an oil-sand mixture

A study was made of oil release by 190 strains of bacteria from a standard crude oil-sand mixture (10% w/w) in 25 x 200 mm glass columns and 20 x l50 mm screw-cap tubes. The bacteria used included 106 halophilic sulfate-reducing anaerobes, 6 fresh-water sulfate-reducing anaerobes, 5 terrestrial anaerobes, 53 marine aerobes, and 20 terrestrial aerobes. Oil release was observed only with the halophilic sulfate -reducing anaerobes, ranging from 2.5 to 5.5% on the sand columns and from 0-52% in the screw-cap tubes. Rates of bacterial migration through the mixtures and surface-tension changes were also studied in an attempt to clarify release mechanisms.