A field demonstration of a quantitative framework for defining the limits on in situ bioremediation

Abstract

Historic cis-dichloroethene (cDCE) groundwater concentrations leaving the Russell Road landfill were greater than Virginia groundwater protection standards. In response, a pilot-scale system was implemented to stimulate reductive dechlorination. In support of this program, this study investigated the utility of a quantitative framework analysis to determine the overall rate-limiting step for in situ bioremediation at the site, based on a set of dimensionless parameters estimated from site-specific, scale-dependent processes. Sorption was determined not to be limiting due to the small magnitude and relatively rapid rate. However, either the biokinetics and/or the horizontal transverse dispersion, DT, processes were predicted to be the rate-limiting step(s) due to the apparently slow biokinetics and low DT value. These conclusions were consistent with the pilot-scale data, which indicated no enhancement of cDCE reduction or injected electron donor in many downgradient wells, demonstrating the potential utility of the dimensionless quantitative decision making framework applied in this work.