Aerobic Cometabolic Biodegradation to Treat Emerging Chemicals and Co-Contaminants in Dilute Plumes

One of the major challenges in managing large dilute plumes is treating recalcitrant emerging contaminants such as 1,4-dioxane (14D), 1,2,3-trichloropropane, and N-Nitroso-dimethylamine. Conventional technologies (e.g., in situ anaerobic bioremediation or ex situ granular carbon adsorption) selected to treat primary contaminants (e.g., chlorinated solvent compounds) are often inadequate to treat emerging contaminants. Aerobic cometabolic biodegradation has been considered a promising remedial technology that can concurrently treat a wide spectrum of organic contaminants to very low concentrations. The feasibility of concurrent treatment of all contaminants via the aerobic cometabolic biodegradation process was demonstrated at the former McClellan Air Force Base site in California. The primary substrates, HD10 propane and oxygen, were added to recirculated groundwater to stimulate the aerobic cometabolic activity of the indigenous microbial population in situ. The treatment results show that 14D can be treated to concentrations below 1 ug/L and co-contaminants trichloroethene, 1,2-dichloroethane, and 1,1dichlorehene can be concurrently treated to their respective analytical method detection limits of 0.23, 0.18, and 0.2 ug/L, respectively. The degrading activity lasts for more than two weeks without the addition of primary substrates, indicating the stability and robustness of the treatment process. The treatment efficiencies are contaminant specific, ranging from 90 to 99%, comparable to the efficiencies observed in other similar field studies that used significantly higher primary substrate loading rates. In this presentation, the insights gained from this demonstration field test will be shared; various potential applications, including different suites of contaminants, various types of substrates, enhanced natural attenuation, and mass flux management will be presented. Finally, implementation of in situ aerobic cometabolic biodegradation under various large dilute plume scenarios will be described.