Modeling biodegradation of organic pollutants during transport through permeable reactive bio-walls

One-dimensional solute transport through a permeable reactive bio-wall (PRB) (i.e., a permeable reactive wall with microbial reagents) is simulated in this study using the advection-dispersion equation with a biodegradation sink term. The biodegradation process is modeled using either linear, first-order kinetics or the Monod non-linear kinetics expression. Solute breakthrough curves for first-order and Monod kinetics are compared for a range of influent pollutant concentrations (c0) and for different values of microbial mass (Mt) using typical PRB design values and Monod growth parameters (μmax, Kc). The results indicate that values of pollutant concentration downgradient of a PRW predicted using first-order and Monod kinetics are similar when c0 is small relative to Kc (ie., when Kc/c0 ≥ 10.0) and/or when Mt is large such that β = μmaxMt/Kc≥ 5.0. However, first-order kinetics provides unconservative estimates of the downgradient concentration for smaller Kc/c0 or β and, therefore, should be used with caution