Modelling of Cometabolic Transformation of ortho-xylene in a Dentrifying Biofilm System

A model describing the cometabolic biotransformation of o-xylene with toluene as primary carbon source in a continuously fed fixed biofilm reactor is presented. The model is based on the concept of competitive inhibition between o-xylene and toluene. The proposed model simulated successfully the transformation of o-xylene and the associated by-products formation, as well as the toluene degradation. However, it appears that an accurate measurement of active biomass density and distribution in the biofilm is needed, since these factors dramatically affects the modelling. The modelling of various kinetic experiments indicates that the active biomass (or toluene degraders) is accumulated on the top of the biofilm, leading to the conclusion that only a minor part of the biofilm thickness was active. The calibrated model is able to predict the removal of toluene and o-xylene for concentrations ranging from 0 to 30 mg/L. For higher concentrations toxicity phenomena may decrease the accuracy of the model.