Two-step modeling of the biodegradation of phenol by an acclimated activated sludge

Phenol biodegradation by an acclimated activated sludge was investigated in batch cultures with variable initial conditions of substrate and biomass (0.10 ? S0/X0 ? 1 g phenol g TSS?1). As conventional Haldane model could not explain the biomass growth observed after phenol exhaustion, a model based on the production and later consumption of an inhibitory metabolic intermediate was developed to describe the phenol biodegradation and the biomass growth profiles. This two-step model considers that biodegradation is accomplished by two microbial populations constituting the whole biomass. The new model depicts successfully both biomass and phenol courses by using a single set of kinetic parameters, and support the notion that the production of metabolic intermediates has a determinant role in phenol biodegradation kinetics.