KINETICS OF BTX BIODEGRADATION AND MINERALIZATION IN BATCH AND COLUMNSYSTEMS

Flow-through column and liquid batch experiments were performed in the present study in order to evaluate whether the kinetics of biodegrada tion reactions of organic contaminants for batch conditions were compa rable to those measured under solid-to-solution ratios applicable to a quifer or water-saturated soil systems. The biodegradation of benzene, toluene, and xylene was observed under oxic conditions. Steady-state reaction rates were determined for the biodegradation reactions in the flow-through columns and evaluated using a rate law based on the Mono d equation for conditions where bacterial growth is negligible. Calcul ated rate constants (k(1)) for biodegradation, or substrate disappeara nce, for sole substrate experiments were 1.32 mmol L(-1) h(-1) for ben zene, 1.42 mmol L(-1) h(-1) for toluene, and 0.833 mmol L(-1) h(-1) fo r xylene. Rate constants were determined for batch experiments using a rate law based on the Monod equation that does account for bacterial growth. The maximum specific growth rate, mu(max), was found to be sim ilar between batch and column experiments, indicating that there were no mass-transport limitations in the columns and that the solid-to-sol ution ratio was not a significant factor affecting kinetic parameters. There is considerable variability in rate constants for BTX biodegrad ation reported in the literature, up to two orders of magnitude for mu (max). Rate constants from this study were within the range of publish ed values. For the experiments reported here, rates determined for sol e carbon sources could be used to predict the reaction rates of BTX mi xtures given some adjustment of cell yields and lag times.