Evaluating the Impact of a Wetland Plant and Rhizosphere Microorganisms on the Fate of a Model Chlorinated Solvent in a Wetland Plant Bioreactor
Becker, Jennifer G
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The ability of wetland plants to impact the removal of cis-1,2-dichloroethene (DCE), an intermediate formed during reductive dehalogenation of tetrachloroethene (PCE) and trichloroethene (TCE), either via phytoremediation or rhizosphere oxidation, which enhances aerobic microbial activity, was investigated. To accomplish this goal, a bench-scale bioreactor system was designed to model wetland conditions and evaluate DCE biodegradation. The bioreactor was operated as a continuous-flow, completely-mixed biofilm reactor containing a single Phragmites australis individual and root associated microorganisms. Significant removal of DCE in the bioreactor was observed. To elucidate the removal mechanisms, the fate of 14[C]-DCE was determined. The predominant removal mechanism was microbially-mediated oxidation, presumably facilitated by plant-supplied oxygen and growth substrates, followed by phytovolatilization, and incorporation into, and/or sorption to, plant and microbial biomass. Based on these results, wetland plants and their associated microorganisms are expected to contribute to DCE removal in the rhizosphere.