Biofilms characteristic of aquifer conditions can be rapidly and efficiently collected using in situ microcosms or bio-traps containing Bio-Sep® beads (25% Nomex and 75% powdered activated carbon (PAC)). Bio-Sep® beads can be baited with a variety of organic compounds by vapor phase adsorption onto the PAC component of the beads under reduced pressure. In the aquifer the bait or amendment does not substantially leach into the aquifer but is available to bacteria as a carbon source within the bead. When the organic compound is labeled with 13C, phospholipids may be extracted from bead biofilms post-incubation and derived fatty acid methyl esters (FAMEs) analyzed for 13C. Incorporation of 13C into biomass provides proof of current in situ biodegradation potential.  We have now baited Bio-Sep® beads with 13C-labeled methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA). Deployment of these 13C-amended bio-traps has been coupled with stable isotope probing to demonstrate the biodegradation of MTBE and TBA in an anaerobic gasoline plume in southern California. Non-amended bio-traps were deployed at the same site as a pre-experiment to determine if spatial variations in microbial ecology could be linked to concentrations of oxygenates or other electron donors. 

Analysis of biofilm phospholipids and DNA from non-amended bio-traps demonstrated a clear relationship between various aspects of the subsurface microbial ecology and the concentration of TBA. There was no correlation of any PLFA or DNA attributes with the concentration of MTBE, BTEX or TPHg. Deployment of 13C5-MTBE or 13C4-TBA amended bio-traps in the plume clearly demonstrated the biodegradation of both MTBE and TBA under aquifer conditions through incorporation of 13C into membrane phospholipids.

Abstract K-027, in: Bruce M. Sass (Conference Chair), Remediation of Chlorinated and Recalcitrant Compounds—2008.  Proceedings of the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey,CA; May 2008). ISBN 1-57477-163-9, published by Battelle, Columbus, OH, www.battelle.org/chlorcon.