Characterization of Chlorinated Ethene Degradation in a Vertical Flow Constructed Wetland

Chlorinated solvents, including perchloroethene (PCE) and trichlorethene (TCE), are among the most common groundwater contaminants found in the United States. Once released into the environment, chlorinated solvents are extremely persistent and often require costly and lengthy remedial actions. The use of constructed wetlands has shown promise as an effective and less costly alternative for the treatment of chlorinated solvent contaminated groundwater. This study characterized and evaluated the concentration of chlorinated ethenes within a vertical flow constructed wetland, fed with PCE contaminated groundwater, at Wright-Patterson Air Force Base (WPAFB), Ohio. Chlorinated ethene concentrations were characterized within three distinct layers of the wetland cell, as well as within the influent, and effluent. In addition, a pore-water sampler prototype was designed and developed for this research effort in order to obtain a more detailed contaminant profile. PCE concentrations declined from an average of 46.5 μg/L in the influent to an average of 0.5 μg/L in the upper layer, a 98.9% decrease. The chlorinated ethene concentration profiles indicate that the lower half of the wetland provides favorable conditions for the complete anaerobic reductive dechlorination of the PCE. Within the upper half of the wetland, contaminant profiles indicate dominant degradation processes other than anaerobic reductive dechlorination, possibly including aerobic or anaerobic oxidation or direct volatization. The limited data generated from the implementation of the pore-water sampler prototypes was inclusive, requiring the need for further testing and research