Influence of chemical surfactants on the biodegradation of crude oil by a mixed bacterial culture

The effects of surfactant physicochemical properties, such as the hydrophil e-lipophile balance (HLB) and molecular structure, on the biodegradation of 2% w/v Bow River crude oil by a mixed-bacterial culture were examined. Via ble counts increased 4.6-fold and total petroleum hydrocarbon (TPH) biodegr adation increased 57% in the presence of Igepal CO-630, a nonylphenol ethox ylate (HLB 13, 0.625 g/L). Only the nonylphenol ethoxylate with an HLB valu e of 13 substantially enhanced biodegradation. The surfactants from other c hemical classes with HLB values of 13 (0.625 g/L) had no effect or were inh ibitory. TPH biodegradation enhancement by Igepal CO-630 occurred at concen trations above the critical micelle concentration. When the effect of surfa ctant on individual oil fractions was examined, the biodegradation enhancem ent for the saturate and aromatic fractions was the same. In all cases, bio degradation resulted in increased resin and asphaltene concentrations. Opti mal surfactant concentrations for TPH biodegradation reduced resin and asph altene formation. Chemical surfactants have the potential to improve crude oil biodegradation in complex microbial systems, and surfactant selection s hould consider factors such as molecular structure, HLB, and surfactant con centration.