A MODELING STUDY OF ANAEROBIC BIOFILM SYSTEMS .1. DETAILED BIOFILM MODELING

A detailed model acetate-utilizing methanogenic biofilms accounting fo r the diffusion of neutral and ionic species, chemical equilibrium, el ectroneutrality, gas production within the biofilm, pH-dependent Monod kinetics, and the presence of a concentration boundary layer is prese nted. The model qualitatively fits the pH profiles that are reported f or acetate-utilizing methanogenic aggregates. A sensitivity analysis o n the biological parameters showed that the flux of acetate is sensiti ve to the maximum utilization rate, half-saturation constant, and biof ilm density for the hulk conditions investigated. Criteria when tradit ional biofilm models can be used to predict the flux of acetate into t he biofilm are established. If the maximum pH change predicted using a hypothetical system is within +/-0.05, the traditional model predicts the flux to within +/-5% of the value calculated with the model devel oped in this study. (C) 1995 John Wiley and Sons, Inc.