Hydrodynamics of Bioreactor Systems for Liquid-Liquid Contacting

Abstract

Two liquid—liquid bioreactors, a stirred-tank and a novel electrostatic-dispersion system, are being used to investigate biodesulfurization of oil by sulfate-reducing bacteria (SRB). The hydrodynamic behavior of both bioreactors under various operating conditions is discussed in this article. The total liquid volume of the stirred-tank system is 1 L in a 1.5-L cylindrical tank equipped with two baffles and two Rushton-type six-blade impellers. The steady-state average drop size (d ₃₂) was determined by a video technique, and correlated with operating conditions, physical properties, and system geometry. Although the stirred-tank geometry was not standard, the d ₃₂correlation was found to be in good agreement with correlations reported in the literature. For the electrostatic dispersion system, a 0.25-L column was used with kerosene as the continuous phase and water containing SRB as the dispersed phase. Microdroplets were obtained by the break-up of the aqueous phase meniscus at the tip of a capillary tube using pulsed direct current (dc) electric fields. The size of the drops ejected from the capillary was measured as a function of the intensity of the applied voltage. Preliminary results showed no deleterious effect of electrospray dispersion on bacteria viability.

Author to whom all correspondence and reprint requests should be addressed. E-mail: tsourisc@ornl.gov