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A COMPARISON OF MOLECULAR AND CULTURAL METHODOLOGIES FOR ENUMERATING BACTERIA IN LANDFILL LEACHATES
Citation:
GROSSER, R. J., B. J. MORRIS, G. A. DAVIS, R. B. GREEN, G. R. HATER, D. A. CARSON, AND W. J. DAVIS-HOOVER. A COMPARISON OF MOLECULAR AND CULTURAL METHODOLOGIES FOR ENUMERATING BACTERIA IN LANDFILL LEACHATES. Presented at Fifth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, May 22 - 25, 2006.
Description:
Landfill bioreactor technology has been under investigation in the field for its potential economic and waste treatment benefits over conventional landfill systems. A better understanding of biological influences on the stabilization process is needed for incorporation into the engineering design, as well as leachate and gas management protocols. This work describes the microbiological characterization component of a Cooperative Research and Development Agreement (CRADA) formed between Waste Management, Inc., and the US EPA, investigating the use of the landfill bioreactors at the field scale. The study site under investigation is the Outer Loop Landfill in Louisville, KY, USA, where two full-scale bioreactor treatments have been established now for over five years. One bioreactor treatment is a converted landfill bioreactor which operates utilizing nitrified-treated collected leachate and recirculating it through the landfill bioreactor cells. An as-constructed landfill bioreactor configuration is also under study in which solid waste is initially aerated in the bioreactor cells followed by liquid addition to promote anaerobic conditions to develop. Quarterly leachate samples were collected from duplicate bioreactor cells, as well as two control cells operated under conventional landfill treatment. Leachate samples were analyzed for elemental/chemical concentrations and numbers of different bacterial functional groups. The functional groups included aerobic, anaerobic, denitrifying, sulfate reducing and methanogenic bacterial groups. Cultural microbiological methods used included standard plate counts from agar surfaces and most probable number (MPN) calculations from selective growth media. Molecular analyses utilized real time PCR (qPCR) methodology for enumerating the different groups of bacteria. Comparisons of the results obtained using both moelcular and cultural methodologies will be presented from over two years of collected quarterly leachate samples.