Field test of limestone as a treatment medium for groundwater at the Savannah River Site


Miles E. Denham, Frank C. Sappington, Gerald C. Blount, and Amy A. Ekechukwu. Savannah River Technology Center, Westinghouse Savannah River Company, Building 773-42A, Savannah River Site, Aiken, SC 29808
Groundwater downgradient from the F- and H-Area Seepage Basins at the Savannah River Site is contaminated with acids, metals, radionuclides, and tritium originally released as part of low-level waste streams from the Separations Areas processing facilities. To stem the flux of tritium discharged from the basin area, a series of wells was installed to extract the groundwater and re-inject it upgradient of the seepage basins. Tritium is captured in an extraction-re-injection cycle that allows it to decay. To meet regulatory criteria for re-injection, metals and radionuclides must be treated and removed. One method under consideration for this removal is in-situ contact with limestone. Equilibration of the groundwater with limestone raises the pH to approximately 8. At this pH, metals and radionuclides can be removed by direct precipitation, co-precipitation, and enhanced adsorption. A pilot test was performed to provide data required to assess the applicability of limestone in groundwater treatment. This demonstration unit consisted of several columns of limestone with different total column lengths and thus different residence times. Ground water from the basins was passed through each of the columns and analyzed for metals, radionuclides, ions, pH, and alkalinity. Results of this field test will be discussed.