Investigation of External Mass Transfer during Biodegradation of Congo Red Dye in a Recirculating Packed Bed Bioreactor

A quantitative investigation of the effect of external mass transfer on the overall rate of biodegradation of Congo Red dye in a recirculating packed bed bioreactor (RPBB) was performed. The isolated Bacillus subtilis MN372379 species was immobilized on the packing material made of low-density polyethylene (LDPE) foam cubes in the RPBB. The overall dye removal rates were measured at varied recirculating flow conditions and an empirical correlation for the external mass transfer coefficient was determined. The observed rate of removal of Congo Red dye in the RPBB was found to be increasing with the recirculation rate. An empirical correlation to predict the non-dimensional Colburn factor was obtained as J(D) = 1.34 Re-0.3. The dimensionless correlation for mass transfer coefficient would enable the design and scale-up of an RPBB with minimal impact of external mass transfer resistance on the overall rate of dye bio-degradation.