Microbial Community Characterization and Pathogen Analysis Within Constructed Wetlands of Varying Scale Designed for Contaminant Removal

Constructed wetlands (CWs) are complex treatment environments, requiring an integrative research approach to improve our understanding of them. The goal of this thesis was to establish an understanding of the functional and structural characteristics of microbial communities within bench-, field- and industrial-scale environmental treatment systems. The impact of pathogenic and/or antibiotic contaminants on these communities based on their functional and structural profiles using community-level physiological profiling (CLPP) and denaturing-gradient gel electrophoresis (DGGE), respectively, was investigated. Under normal operation, bench-, field- and industrial-scale treatment systems were able to produce similarly behaving structural and functional profiles. Increased retention time was consistently associated with communities with low functional capacity and diverse structural properties when compared to areas that initially received pre-treated or untreated wastewater. This indicates that smaller-scale treatment systems may be able to provide similar environments to those in larger-scale treatment systems. However, the normal community profile was not maintained during antibiotic treatment. Based on the metrics used, functional fingerprints displayed metabolic increases after acute addition of antibiotic, which was then followed by a return to preexposure profiles. Conversely, structural fingerprints displayed no acute response, but instead alluded to delayed changes in the proportional abundance of different populations. In addition, the profile was reversed following exposure to untreated industrial wastewater, whereby an increased functional capacity and lowered structural properties were observed. These findings illustrate the dynamic and complex nature of microbial communities in response to selected environmental contaminants.