Treatability Testing of an In Situ Bio-stimulation Barrier for Nitrate and Chromium Treatment

An ongoing treatability test is evaluating in situ bio-stimulation at the 100-D Area of the Hanford Site in Richland, Washington. This test is part of a strategy to couple multiple technologies to accelerate cleanup of hexavalent-chromium contaminated groundwater discharging into the Columbia River. A permeable chemical reducing barrier was previously applied as the primary treatment to prevent the chromium plume from reaching the river at concentrations that exceed regulatory standards. In situ bio-stimulation is intended to provide supplemental treatment up-gradient of this chemical treatment barrier by reducing the concentration of the primary oxidizing species in groundwater (i.e., nitrate and dissolved oxygen) and chromium, thereby increasing the longevity of the chemical barrier and helping to diminish the chromium plume. (authors)