The effects of biofilm characteristics on the external mass transfer coefficient in a differential fluidized bed biofilm reactor

A differential fluidized bed biofilm reactor ( DFBBR) was used for the firs t time to evaluate the external mass transfer coefficient of phenol for a s pherical bioparticle of Pseudomonas putida. The reaction kinetics in the bi ofilm was maintained at first order and respective culture kinetic paramete rs were assessed from a set of continuous fermenter experiments. The fluidi zed bed was operated under nearly fixed hydrodynamic conditions such as bed porosity and fluidization rate to study only the effects of biofilm thickn ess and density on mass transfer. The mass transfer coefficient was calcula ted with the analytical solution of effectiveness factor for the bioparticl e using density-dependent effective diffusion coefficient. The results of t he study revealed that the mass transfer coefficient increased with biofilm thickness at decreasing biofilm density values, which could not have been predicted by correlations in the literature. This increase may be attribute d to increasing porosity and roughness of the biofilm surface. (C) 1998 Els evier Science S.A.