Sustained Bacterial Reduction of CoIIIEDTA- in the Presence of Competing Geochemical Oxidation during Dynamic Flow

Abstract

Radionuclides and metals can be mobilized by chelating agents typically present in low-level radioactive liquid wastes. [60Co]EDTA in the form 60CoIIIEDTA- represents a highly stable [log KCo(III)EDTA = 43.9] and mobile form of this radionuclide. By contrast, the reduced form of this metal−ligand complex, 60CoIIEDTA2-, is much less stable [log KCo(II)EDTA = 18.3] and less mobile. There is an increasing awareness that dissimilatory metal-reducing bacteria (DMRB) can be used to mediate redox transformations of metals and radionuclides whose stability and mobility are governed by their oxidation state. We conducted a series of column experiments to provide an improved understanding of CoIIIEDTA- reduction by the facultative anaerobe Shewanella alga BrY (BrY). Experiments were conducted under growth conditions using lactate as a carbon and energy source. We were able to demonstrate the sustained reduction of CoIIIEDTA- in column flow experiments with the desired result that a less stable, less mobile product ...