The efficacy of wetland treatment systems used to treat runoff mixtures from different landscapes across Kentucky

Document Type

Dissertation

Abstract

The overarching goal was to improve our understanding of the cumulative effect of increased use and occurrence of commonly detected contaminants of potential concern (CPCs) on nitrogen (N) transformation processes in wetlands. The central hypothesis was that those various mixtures of nutrients and CPCs entering treatment wetlands impact N removal pathways. The first study assessed the current state of the literature on the implications to N removal in wetlands in the presence of pesticides and antibiotics. 181 primary studies were identified. Removal efficiencies for nitrate varied widely across the studies, with CPCs impacting microbial communities. A knowledge gap remains in how wetlands are used to treat CPC mixtures resulting in an unknown regarding N removal efficiency. The second study sought to characterize the CPCs appearing in streams in Kentucky, USA. CPCs were found to vary by location, season, and flood conditions. The third study researched the impact that Kentucky’s CPCs have on nitrate removal. Two constructed wetland designs, floating treatment wetlands (FTWs), and free-water surface wetlands (FWSs), were evaluated. Nitrate removal was found to be inhibited in the presence of individual contaminants and FWS N removal was significantly impacted by the presence of contaminant mixtures. The fourth study analyzed the implications of CPC mixtures to N removal by utilizing 15N enrichments to identify specific pathways for nitrate in FWSs and FTWs. While both wetland designs were found to be viable treatment options, differences in management and maintenance plans are needed since the FTWs accumulated more N and CPC in their biomass. This research helped to reveal the black box of N removal transformations in two constructed wetlands positioned in a variety of landscapes (e.g., urban, rural). Findings were developed into two extension documents included in this dissertation.

DOI

https://doi.org/10.13023/etd.2024.277

Publication Date

8-2024

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