Uranium and technetium bio-immobilization in intermediate-scale physical models of an in situ bio-barrier

Graduation date: 2007Metal and hydrogen ion acidity and extreme nitrate concentrations typical of\ud Department of Energy (DOE) legacy waste sites pose formidable challenges to\ud successful implementation of in situ bio-immobilization. Intermediate-scale (~ 2.5 m),\ud flow through models of an in situ bio-barrier were constructed to investigate U and Tc\ud removal from groundwater at a contaminated site in Oak Ridge, TN. In one study,\ud ethanol additions to pH-neutral contaminated site groundwater, flowing through a\ud mixture of site sediment and crushed limestone, effectively stimulated iron- and sulfatereducing\ud conditions and sustained U and Tc removal for 20 months. In a related study,\ud ethanol additions to nitric acid contaminated site groundwater, flowing through a\ud mixture of site sediment and crushed limestone, effectively promoted denitrification for\ud over 20 months. A combined signature lipid and nucleic acid-based approach was used\ud to spatially characterize microbial communities at relatively small spatial scales (