Effects of microcosm preparation on rates of toluene biodegradation under denitrifying conditions

Microcosms were prepared with subsurface material from two aquifers to examine the effects of preparation methods on rates of toluene biodegradation under denitrifying conditions. In both cases, the data fit a zero-order kinetics plot. However, rates of removal were generally proportional to initial toluene concentrations, resulting in similar half-lives. Increasing the solid/liquid mass ratio resulted in decreased lag times in one aquifer material, although in both cases the specific toluene mass removal rate (g toluene g sediment-1 day-1) also decreased. Varying either the initial toluene concentrations or the solid/liquid ratios by two to three orders of magnitude resulted in a half-life variation of only a factor of two, with most of the differences occurring at the extreme ranges of the test variables. These data indicate that similar biodegradation rates might be expected from microcosms prepared with different contaminant concentrations and solid/liquid ratios, which is useful for design of microcosm studies to evaluate biodegradation at field sites.