Comparison of biodegradation kinetic parameters for naphthalene in batch and sand column systems by Pseudomonas putida

Kinetic parameters for the degradation of naphthalene by Pseudomonas putida (ATCC 17484) were estimated in both batch and column assays, in order to e valuate the role of flow, and cell attachment on biodegradation rates. Susp ended cells and cells attached to Ottawa sand were used under a variety, of biomass levels, column flow-rates, and substrate concentrations. In batch systems, degradation followed zero-order kinetics across the entire concent ration range, while the columns exhibited decreased rates at concentrations less than 100 (mug/L), describable by Michaelis-Menten kinetics. This is r eflected in elevated values of the half-saturation constant, K, in columns. We offer the explanation that this may, have resulted from reactive hetero geneity, within the porous media, imposing a distribution of length-scales for transfer of substrate to the cell surfaces. Well-mixed batch systems ar e expected to have both shorter and more uniform transfer distances. When k inetic parameters obtained in batch system are used for prediction of degra dation in columns, at least two factors-exposed reduction of exposed cell s urface area and heterogeneity of cell distribution-will likely, reduce over all column degradation rates.