The present study details the derivation and application of a finite-volume-based methodology to the simulation of biofilm processes in axisymmetric reactors. Multiple space scales, ranging from the micron to the meter, and multiple time scales, ranging from the second to the day, are resolved. Unsteady problems are considered, where diffusion and biochemical reactions are the dominant physical phenomena. Moreover, moving boundaries such as the interface between biofilm and bulk liquid are accounted for. Numerical results are presented for a few test cases, and the sensitivity of the predictions to several numerical and physical parameters is studied, including time step value, number of iterations per time step, grid size, and initial conditions. © 1993 Academic Press, Inc.