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

Abstract

A differential fluidized bed biofilm reactor (DFBBR) was used for the first time to evaluate the external mass transfer coefficient of phenol for a spherical bioparticle of Pseudomonas putida. The reaction kinetics in the biofilm was maintained at first order and respective culture kinetic parameters were assessed from a set of continuous fermenter experiments. The fluidized bed was operated under nearly fixed hydrodynamic conditions such as bed porosity and fluidization rate to study only the effects of biofilm thickness and density on mass transfer. The mass transfer coefficient was calculated with the analytical solution of effectiveness factor for the bioparticle using density-dependent effective diffusion coefficient. The results of the 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 attributed to increasing porosity and roughness of the biofilm surface.