A quantitative analysis of external mass transfer combined with a biodegradation reaction and correlation of the experiment with theory was performed for phenol removal using calcium-alginate gel-immobilized P. putida in a packed-bed column reactor Assuming first-order biodegradation kinetics, pseudo first-order biodegradation rate constants (k(p)) were calculated. To investigate the effect of external film diffusion on the biodegradation rate, various mass transfer correlation models of the type j(D) = KNRe-(l-n) were systematically tested and the mass transfer coefficients (k(m)) were calculated as a function of the mass flux (G) and the Reynolds number (N-Re) at different n values. The intrinsic first-order biodegradation rate constants (k) and the surface areas per unit weight of dried cells for mass transfer (A(m)) were determined from 1/k(p) vs. I/G(n) plots at the same n values. Finally, combining the k values with k(m)A(m) values, the pseudo first-order biodegradation rate constants (k(p)) were calculated again and compared with the k(p) values determined from experimental data; thus, it was decided that the mass transfer correlation j(D) = 1.625 Re-0.507 accurately predicted our experimental data.