Microbial enhanced separation of oil from a petroleum refinery sludge

Petroleum refineries around the world have adopted different technological options to manage the solid wastes generated during the refining process and stocking of crude oil. These include physical, chemical and biological treatment methods. In this investigation bacterial mediated oil separation is effected. Two strains of Bacillus were isolated from petroleum-contaminated soils, and inoculated into slurry of sludge, and sludge-sand combinations. The bacteria could effect the separation of oil so as to form a floating scum within 48 h with an efficiency of 97% at ≤5% level of sludge in the sludge-sand mixture. The activity was traced to the production of biosurfactants by bacteria.