Technology Description

MNA relies on natural processes such as dispersion and biological degradation to reduce contaminant concentrations to acceptable levels without human intervention. The natural attenuation mechanism that is the main focus of MNA regulatory documents to date is anaerobic reductive dechlorination (ARD). For many years at a number of sites, it was thought that ARD was the only viable mechanism for MNA. However, due to the large size and general aerobic conditions of many of the plumes where MNA would be a viable option and ARD is not feasible, other biological mechanisms have received a great deal of research interest in more recent years, including direct oxidative and cometabolic processes. The primary focus of this project is aerobic cometabolic processes. Microcosm studies will be performed on samples collected from TCE-contaminated aquifers and will combine enzyme activity probes specific for aerobic oxygenase enzymes, molecular techniques such as polymerase chain reaction (PCR) amplification and fluorescent in situ hybridization (FISH) to provide evidence in support of enzyme activity probes, and contaminant transformation measurements to determine the rates of TCE cometabolism. The project will provide a comprehensive assessment of active aerobic degradation mechanisms at each demonstration site, as well as an estimate of the rate of contaminant degradation.