Characterization of Chlorinated Solvent Degradation in a Constructed Wetland

Widespread chlorinated ethene contamination of aquifers coupled with high costs of current treatment technologies demand innovative remediation solutions. Wetlands, maintaining anaerobic and aerobic zones promoting the complete degradation of chlorinated ethenes such as Tetrachloroethylene (PCE), could be the answer. This thesis characterized the chlorinated solvent contamination levels in three strata of an upward flow constructed wetland. Analysis of samples was accomplished by purge-and-trap gas chromatography. Water quality parameters, Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP), pH, Conductivity, and Temperature, were also measured in monitoring wells with a water monitoring sonde. After removing data outliers caused by short-circuiting flow, PCE concentrations declined from an average of 32,59 ± 0,699 ppb (± 95% confidence interval) in the inflow stream to an average of 0.171 ± 0.079 ppb in the upper layer (99,3% reduction). Concentration trends of PCE degradation products cis-1,1 -Dichloroethylene (cis-DCE), Vinyl Chloride (VC), and Trichloroethylene TCE) indicate dechlorination processes are occurring. In addition to PCE, TCE at concentrations below 0,6 ppb was the only other analyte detected in the inflow and outflow, Water quality measurements (DO and 0RP) decreased from the bottom to the middle layer to a level that supports anaerobic reductive dechlorination but not methanogenesis. The DO increased slightly from the middle to the top layer while 0RP continued to decrease