Floating Treatment Wetlands: Inter-Relationships between Engineered Solutions for Nutrient Pollution and their Bodies of Water

Abstract

Floating treatment wetlands (FTWs) are a best management practice (BMP) currently used in several countries worldwide to reduce nutrient concentrations in bodies of water. This study examines the chlorophyll-a reduction potential of FTWs in two bodies of water within Minnesota. Field measurements were taken to determine the physical and chemical characteristics of the water affected by the FTWs. Results indicate that the FTWs influence the water close to them but impacts on the entire body of water depend on the percent of the surface area covered by FTWs. FTWs were examined in two additional field sites to determine possible accumulation of periphyton mass on the FTW matrix over time. In both field sites, periphyton was found to accumulate at a relatively constant rate. In addition, the resilience of the FTWs to harsh winter conditions, as they would experience in Minnesota, was tested in a laboratory study. This study put the FTWs through repeated freeze-thaw cycles to estimate degradation of the FTW matrix material due to ice stress. A mathematical model was created to estimate the loss of material from the FTWs after a given number of freeze-thaw cycles, and the majority of the losses were found to occur during the freeze-thaw cycles. Further research on these subjects is recommended based on the findings from these experiments.