HYDRODYNAMICS OF BIOREACTOR SYSTEMS FOR LIQUID-LIQUID CONTACTING

Two liquid-liquid bioreactors, a stirred-tank and a novel electrostati c-dispersion system, are being used to investigate biodesulfurization of oil by sulfate-reducing bacteria (SRB). The hydrodynamic behavior o f 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 Rushto n-type six-blade impellers. The steady-state average drop size (d(32)) was determined by a video technique, and correlated with operating co nditions, physical properties, and system geometry. Although the stirr ed-tank geometry was not standard, the d(32) correlation 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 ke rosene as the continuous phase and water containing SRB as the dispers ed phase. Microdroplets were obtained by the break-up of the aqueous p hase meniscus at the tip of a capillary tube using pulsed direct curre nt (dc) electric fields. The size of the drops ejected from the capill ary was measured as a function of the intensity of the applied voltage . Preliminary results showed no deleterious effect of electrospray dis persion on bacteria viability.