Floating Treatment Wetlands in a Northern Climate: Examination of Phosphorus and Nitrogen Removal

Abstract

Excess phosphorus is the largest contributor to nutrient impairment in Minnesota waters. Floating treatment wetlands (FTWs) are a novel best management practice (BMP) to reduce excess nutrients in waterbodies. This study examines the nutrient reduction efficiency of floating treatment wetlands in a northern climate under agricultural loading conditions. A field-based, mesocosm study was completed to quantify the removal efficiency of total phosphorus, Orthophosphate-P, Nitrate-N, and Ammonia-N. The FTWs were each planted with wetland plants Juncus effusus, Eleocharis acicularis, and Glyceria canadensis. A system phosphorus budget was prepared to identify phosphorus sources and sinks within the BMP. Floating treatment wetlands had higher total phosphorus reduction efficiencies. Eleocharis acicularis had the fastest growth rate and highest removal efficiency of the three plants studied. Mesocosms with FTWs had statistically significant lower pH and dissolved oxygen concentrations. Further research areas and FTW design improvements are recommended based on findings from this experiment.