Field Evaluation of a Constructed Floating Wetland for Nutrients and PFAS Attenuation in a Treatment Lagoon

Constructed floating wetlands (CFWs) provide a passive pathway for the retention and accumulation of nutrients and perfluoroalkyl and polyfluoroalkyl substances (PFAS) present in treated wastewater (TWW). This two-year field-scale study investigated the accumulation of PFAS and nutrients in three native wetland species in a lagoon setting. During the plant establishment period and despite measurable nutrient and PFAS uptake in plant tissues, their removal from the water was limited due to short residence times (∼10–12 h). The highest nutrient accumulation in shoots was observed in Phragmites australis (0.14 g N/m2/day and 0.02 g P/m2/day), which showed the highest biomass (12.1 g/m2/day). Phragmites australis also exhibited the highest PFAS and precursor accumulation in tissues. PFAS removal improved after plant establishment, and the daily removal rate for PFAS (based on PFAS accumulation in plant tissue and sediment) was 240 ng/m2/d. Overall, CFWs show promise as a passive, modular solution for PFAS reduction in TWW, particularly after root system development and biofilm formation. However, long-term monitoring across multiple growth and harvest cycles and assessing the contribution of other mechanisms (such as sorption to growth media and accumulation in biofilms) are required to evaluate the CFW system sustainability under varying environmental conditions.