Mechanisms of biofilm detachment in anaerobic fluidized bed reactors

Biofilm growth and detachment mechanisms in anaerobic fluidized bed reactors (AFBRs) were studied. The hydrodynamic characteristics and the energy dissipation of the biological fluidized bed were investigated. Biofilm growth experiments in a pilot-scale AFBR were performed and attached biomass concentration was observed to increase rapidly in the upper part of the bed. The measured and predicted biomass concentrations showed good agreement. Biomass loss due to hydrodynamic forces and particle collisions were also investigated during the experimental studies. Some relationships applicable to the AFBRs were obtained for the biofilm specific detachment rate (r(b)) versus the fraction solids (C-v), the hydrodynamic shear stress (tau) and the Reynolds number of the flow (Re) with good accuracy. Detachment rate increased with the increment in C-v and tau and decreased with increase of Re. It was found that the shear stress and particle collisions play a major role in the detachment mechanism.