Kinetics of Toluene Degradation by Denitrifying Aquifer Microorganisms

The kinetics of toluene degradation by denitrifying aquifer microorganisms and the resulting biomass production were adequately characterized by Monod's equation. Toluene degradation was stoichiometrically coupled to nitrate reduction and biomass production. The estimated biokinetic parameters (Y = 0.6 g cells/g toluene; k = 0.28 g toluene/g cells/day; and Ks = 8.6 mg toluene/L) were tested in an independent kinetic experiment with a much lower initial denitrifier concentration. Simulations were in reasonable agreement with the observed toluene degradation pattern, and illustrated the strong dependence of the degradation time on the initial active biomass concentration. Monod coefficients are system-specific, and caution should be exercised in extrapolating values measured in a given environment to another. Factors that contribute to the wide variability of reported coefficients include the metabolic diversity of microbes isolated from different systems, variations in environmental conditions, and the different experimental and analytical procedures used in their determination.