Biosurfactant-enhanced degradation of residual hydrocarbons from ship bilge wastes

Abstract

The use of Bacillus subtilis O9 biosurfactant (surfactin) and of bioaugmentation to improve the treatment of residual hydrocarbons from ship bilge wastes was studied. A biodegradation experiment was conducted in aquaria placed outdoors under non-aseptic conditions. Three treatments were examined: culture medium plus bilge wastes, bioaugmentation with microorganisms from bilge wastes, and bioaugmentation plus biosurfactant. Samples were analyzed for viable counts, aliphatic and aromatic hydrocarbon concentrations, n-C17/pristane and n-C18/phytane ratios. While the addition of biosurfactant stimulated hydrocarbon degradation, bioaugmentation did not produce any remarkable effect. At day 10, the remaining percentages of aliphatic and aromatic hydrocarbons in aquaria, which received biosurfactant, were 6.8 and 7.2, respectively, while it took 20 days to reach comparable results with the other treatments. The biosurfactant did not affect the preferential biodegradation of n-C17/pristane and n-C18/phytane. This biosurfactant, which can be produced in a relatively simple and inexpensive process, is a promising alternative in the optimization of hydrocarbon waste treatment.