MECHANISMS OF BIOFILM DETACHMENT IN FLUIDIZED-BED REACTORS

Biofilm detachment in liquid fluidized bed biological reactors was inv estigated to point out how different mechanisms influence the process. Erosion due to liquid shear and abrasion due to collisions of particl es were considered as possible mechanisms of biomass detachment in liq uid fluidized beds. A dimensional analysis technique allowed the ident ification of the significant parameters affecting the process. The inf luence of these parameters was established on a lab-scale reactor. An empirical model was proposed to correlate the experimental data and to analyze the effect of some characteristic quantities, such as particl e Reynolds number, biomass fraction, liquid shear stress and solid con centration, on the detachment rate. Detachment rate strongly increased with fluid velocity while, owing to modifications in biofilm structur e and morphology during the biological growth, it slightly decreased w ith liquid shear stress. (C) 1997 IAWQ. Published by Elsevier Science Ltd.