Microbial Insights

In Situ Microcosm Studies to Quantitatively Compare MNA, Biostimulation, and Bioaugmentation as Corrective Actions at PCE-Impacted Sites

Brett Baldwin, Greg Davis, Dora Ogles, and Anita Biernacki (Microbial Insights), Aaron Peacock (Haley & Aldrich), Duane Graves (Geosyntec), Kerry Sublette (University of Tulsa)

Traditionally laboratory microcosms and small-scale pilot studies have been used to investigate the feasibility of bioremediation as a corrective action and to screen remedial approaches at sites impacted by chlorinated solvents. However, duplication of in situ conditions in the laboratory is difficult and the results often do not correlate to the field. Pilot studies are performed in the field but can be prohibitively expensive as an investigative tool. In the current study, three distinct Bio-Trap Samplers, each corresponding to one of the most common remedial alternatives (MNA, biostimulation, and bioaugmentation), were deployed in each study well. As the names suggest, the MNA unit contained no electron donor, the Biostimulation unit contained a commercial electron donor, and the Bioaugmentation unit was pre-inoculated with a commercial Dehalococcoides culture and was supplemented with an electron donor. All three Bio-Trap units contained passive diffusion VOC and anion samplers for chemical and geochemical analyses. Following in-well deployment, qPCR enumeration of Dehalococcoides and vinyl chloride reductase genes was used to assess the ability of each treatment alternative to support or stimulate growth of halorespiring bacteria. The VOC and anion samplers were used to determine concentrations of parent compounds, daughter products, dissolved gases, terminal electron acceptors, volatile fatty acids, and chloride. In total, the Bio-Trap in situ microcosm study integrated microbiological, chemical, and geochemical lines of evidence to evaluate three remedial alternatives in a single in situ pilot study providing results used to direct subsequent site management activities.

Abstract L-41, in: G.B. Wickramanayake and H.V. Rectanus (Chairs), In Situ and On-Site Bioremediation—2009. Tenth International In Situ and On-Site Bioremediation Symposium (Baltimore, MD; May 5–8, 2009). ISBN 978-0-9819730-1-2.Publisher: Battelle Memorial Institute, Columbus, OH. www.battelle.org/biosymp