A New Model of Phenol Biodegradation and Activated Sludge Growth in Fedbatch Cultures

Phenol biodegradation using acclimated activated sludge was investigated in batch and fedbatch cultures with variable initial concentrations of phenol and biomass. The batch experimental data show a cell growth after phenol exhaustion, making the use of a conventional Haldane model, for which specific growth rate μ = 0 when substrate S = 0, inadequate to describe biomass growth profiles. On the other hand, the fedbatch experiments have shown enhanced inhibitory effects on phenol degradation when compared to batch cultures. Both phenomena were attributed to the metabolic intermediates accumulation and to their later consumption during phenol degradation. Consequently, a new Haldane-based model that explicitly integrates the kinetic evolution of a main intermediate was designed. The model allowed accurate predictions of both phenol and biomass concentration courses in both operating modes over a wide range of initial conditions.