The overall goal of the research program was to provide new fundamental data and numerical simulations to assess the impact of bioreductive remedial processes on rates and mechanisms of colloid generation and the subsequent impact on contaminant co-transport, as well as the propensity for irreversible changes in soil structure following bioremediation. Specific objectives included:
The objectives were resolved by a technical approach that included three well-integrated experimental tasks, as follows:
Tasks A and C were largely addressed by the previous research team and results are summarized as follows:
Task B was largely addressed by the substitute project team and results are summarized as follows:
For colloid generation and pore accessibility, the microbially mediated Fe(III)-oxide reduction was demonstrated in this project to have significant effect on the transport of molecular and colloidal tracers and colloid generation, depending on the duration of the bioreduction process. For bioreduction and re-oxidation, this project showed that electron-donor addition during biostimulation cannot continue indefinitely. Thus, upon termination of biostimulation, the treated area will ultimately return to its original redox status as oxygenated groundwater passes through the treatment zone.
Hansel, C.M., C.J. Lentini, Y. Tang, D.T. Johnston, S.D. Wankel, and P.M. Jardine. 2015. Dominance of Sulfur-Fueled Iron oxide Reduction in Low-Sulfate Freshwater Sediments. ISME J, 10.1038(20115.50):1-13.