Effect of viscosity of nonaqueous-phase liquids (NAPLs) on biodegradation of NAPL constituents

A study was conducted to evaluate the effect of viscosity of nonaqueous-phase liquids (NAPLs) on biodegradation of phenanthrene in soil slurries and to find means to enhance the process in viscous NAPLs. When present in kerosene, diesel fuel, fuel oil, and mixtures of the NAPLs, phenanthrene was biodegraded rapidly. Gasoline alone or in mixtures with other solvents prolonged the acclimation phase and reduced the rate of mineralization of the hydrocarbon. The rate and extent of biodegradation decreased with increasing viscosity of nontoxic NAPLs. The slow mineralization of phenanthrene initially in 150 Bright stock or crude oils was enhanced by vigorous agitation of soil slurries, addition of a nonionic surfactant and delayed inoculation, or increasing the temperature. The data suggest means for enhanced bioremediation of toxicants present in viscous NAPLs