Finite Difference Simulation of Cr(VI) Reduction and Cr(VI) Concentration Profiles in Aquifer Microcosm Columns

Abstract

This study is an initial step towards the development of an in situ bioremediation process to prevent the spread of Cr(VI) in groundwater aquifers. The study was conducted using columns with five sampling ports along the length. Cr(VI) concentration was  measured in the influent, in five equally spaced intermediate ports within the column and in the effluent, to facilitate spatial modelling of Cr(VI) concentration profiles within the column. Four Cr(VI) feed concentrations: 20, 30, 40, and 50 mg.L-1, were evaluated. Near complete Cr(VI) removal was achieved in less than 4 days in the inoculated reactor with organic carbon source at an initial Cr(VI) concentration of 20 mg.L-1, whereas only 69.5% of Cr(VI) removal was achieved at 20 mg.L-1 in an inoculated column without organic carbon source after 4 days of operation. The transport of Cr(VI) across the reactor was determined to be coupled to adsorption and non-competitive inhibited reaction kinetics. However, the effects of the physical chemical processes ( adsorption and biosorption ( diminished in comparison with reaction rate during long-term operation. Cr(VI) reduction kinetics in anaerobic batch studies followed the non-competitively inhibition rate kinetics with km =0.132 mg.L-1, Kc = 672.0935 mg.L-1, Rc = 0.0390947 mg.mg-1 and Cr = 100 mg.L-1. Biological reduction of Cr(VI) across the columns was simulate by a one dimensional dispersion-reaction model. The predicted values from this model were then compared with experimental results for validation.
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