Modeling Biooxidation of Iron in Packed-Bed Reactor

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Abstract
A model based on Monod kinetics and originally developed for use with rotating biological contactors was modified for use with a packed-bed column reactor. The reactor was filled with expanded polystyrene beads to immobilize chemolithotrophic bacteria and fed up to 570 mg L−1 (∼10 mM) ferrous iron [Fe(II)] in simulated acid mine drainage. A tracer study indicated changing behavior as a function of hydraulic residence time (HRT), with a transition from complete mix flow behavior to plug flow behavior as HRT decreased. The Fe(II) oxidation efficiency exceeded 95% until the HRT was reduced below 0.5 h. The reactor performance could be predicted with the model using estimates from the literature for û and Y. The experimentally determined half-saturation constant Ks was found to range from 5 to 12 mg L−1. The maximum volumetric capacity constant Rmax was estimated to be ∼360 mg Fe(II)h−1 L−1 beads under complete mix flow conditions but appeared to be as high as 724 mg Fe(II)h−1 L−1 beads as conditions approached plug flow at short HRTs.