Population dynamics of tetrachloroethene dechlorinating consortia for surfactant and bioaugmentation remediation applications
Daprato, Rebecca C.
Hughes, Joseph B.
Doctor of Philosophy
Three anaerobic, dechlorinating consortia were enriched from different origins using methanol and tetrachloroethene (PCE) and maintained for approximately three years. Characterization of the consortia with terminal restriction fragment length polymorphism (TRFLP) and qualitative and quantitative PCR (qPCR) demonstrated that all three dechlorinating communities were dominated by Dehalococcoides and Dehalobacter spp. Monitoring methane production combined with qPCR for archaea demonstrated that complete PCE dechlorination occurred in the presence and absence of methanogenesis. Combining results for denaturing gradient gel electrophoresis (DGGE) and qPCR for reductive dehalogenase genes suggested that one consortium contained a strain 195-type organism with the ability to respire vinyl chloride (VC). The effect of the anionic surfactant SteolRTM CS-330 on PCE dechlorination was evaluated using pure and mixed dechlorinating cultures. Sulfurospirillum multivorans was the only pure culture able to dechlorinate in the presence of SteolRTM CS-330. S. multivorans was present in consortia OW and CH, and these consortia were capable of partial dechlorination to cis-dichloroethene ( cis-DCE) in the presence of SteolRTM CS-330. Monitoring Dehalobacter spp., Sulfurospirillum spp. and Dehalococcoides cell numbers in consortium OW during exposure to SteolRTM CS-330 with qPCR demonstrated that the cell numbers were reduced by 79%, 88% and 99%, respectively. Dechlorination past cis-DCE was never recovered after resuspension into surfactant free media. Two experimental controlled release systems (ECRS) were employed to examine PCE source zone bioremediation and the efficacy of bioaugmentation. Results obtained demonstrated that bioaugmentation enhanced PCE removal by a factor of 1.6 over biostimulation alone, but minimal ethene production was observed in both systems. Interestingly, both systems contained Dehalococcoides capable of growth on VC; but VC dechlorination was not observed. It was also demonstrated that the bioaugmented populations became dominant, and that the dechlorinating organisms were not washed out of either system. Analysis of energy flow demonstrated that the dechlorinating populations consumed more energy than the methanogens until chloroethenes became limiting. A comparison of cell numbers between archaea and dechlorinating organisms showed that cell numbers did not correlate to activity, since methanogens had higher cell numbers throughout the experiment.