, Volume 16, Issue 2, pp 413-418

Enhancement of mass transfer characteristics and phenanthrene degradation in a two-phase partitioning bioreactor equipped with internal static mixers

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Abstract

Oxygen and substrate supply have always been considered physical constraints for the performance and operation of two-phase partitioning bioreactors (TPPB), widely used for the degradation of hydrophobic substrates. In this regard, the potential advantages of static mixers in upgrading the oxygen transfer and liquid-liquid dispersions in TPPB have been highlighted. In the present paper, the concomitant influence of static mixers on the gas-liquid mass transfer coefficient k L a and on substrate bioavailability was examined in TPPB. The static method based on conventional forms was developed to estimate the oxygen volumetric mass transfer coefficient. Over a broad range of liquid and air flow rates, the presence of static mixers was found to significantly enhance k L a relative to a mixer-free mode of operation. For identical conditions, static mixers improved the k L a threefold. In the presence of external aeration supply, the boost in the k L a was associated with an increase of 16% in the phenanthrene biodegradation rate due to bubble break up accomplished by the static mixers. On the other hand, static mixers were efficient in enhancing substrate bioavailability by improving the liquid-liquid interfacial area. This effect was reflected by a threefold increase in the degradation rate in the bioreactors with no external supply of air when equipped with static mixers.