Monday, July 30, 2007 - 10:15 AM
S16
Molecular Analysis of PCE DNAPL Source Zone Bioremediation
Rebecca C. Daprato1, Marcio Da Silva2, C. Herb Ward2, Pedro J.J. Alvarez2, and Joseph B. Hughes3. (1) Geosyntec Consultants, 6770 South Washington Ave, Titusville, FL 32780, (2) Civil and Environmental Engineering, Rice University, 6100 Main St, Houston, TX 77005, (3) School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Dr NW, Atlanta, GA 30332
Two experimental controlled release systems (ECRS) were employed to compare biostimulation alone to bioaugmentation and biostimulation for the remediation of a tetrachloroethene (PCE) dense non-aqueous phase liquid (DNAPL) source zone. Quantitative real time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE) with both universal bacterial primers and Dehalococcoides-specific primers were used to investigate the community structure of both systems. Samples were taken before the ECRS was bioaugmented to evaluate the native population present, a second sample was taken on Day 161 of the operation when both systems had primarily cis-DCE in the effluent, and a final sample was taken at the end of the experiment (Day 278). It was determined that Dehalococcoides was an indigenous population in the sand of both tanks, was in the consortium used for bioaugmentation, and was capable of growth on vinyl chloride despite the lack of dechlorination to ethene. DGGE analysis demonstrated that the bioaugmented populations became dominant, and that the dechlorinating organisms were not washed out of either system. Analysis of energy flow to the methanogenic organisms and the dechlorinating organisms demonstrated that the dechlorinating populations consumed more reducing equivalents than the methanogens until the electron acceptor (chloroethenes) became limiting. Comparison of cell numbers between archaea and dechlorinating organisms showed that cell numbers do not correlate to activity, since methanogens had higher cell numbers throughout the experiment. It was also determined that the dechlorinating populations were approximately 1% of the overall community (by cell numbers) in both the bioaugmented and biostimulated systems.