External mass transfer effects were analyzed for removal of carbohydrate and protein by immobilized activated sludge culture in a packed bed bioreactor. The bioreactor was made from 52 cm glass tubing with 5.0 cm inner diameter (with a total volume of 1020 cm(3)). The microbial culture was immobilized on microporus polyurethane cut into cubic pieces of approximately 1.5 cm in length. The effect of flow rate on mass transfer and removal of carbohydrate and protein were analyzed theoretically and compared with experimental data. The rate constants were estimated using external film diffusion models at different flow rates (900, 1200, 1800 cm(3)h(-1)). Based on the experimental data, correlations between the Colburn factor (J(D)) and Reynolds number (Re) as J(D)=5.7 × Re(-0.90) and J(D)=5.7 × Re(-0.18) were found to be adequate to predict the removal of carbohydrate and protein, respectively.
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