Floating Treatment Wetlands for Emerging Contaminants in Wastewater: A Critical Review of Removal Mechanisms, Performance and Sustainability

Floating treatment wetlands (FTWs) are buoyant, vegetated treatment systems in which plant roots and associated biofilms develop directly within the water column. They are increasingly presented as low-energy, modular nature-based technologies for polishing wastewater and contaminated surface waters, yet their capacity to manage emerging contaminants remains less certain than their performance for nutrients, suspended solids and some conventional pollutants. This critical narrative review evaluates evidence for removal of pharmaceuticals and personal care products, antibiotics, pesticides, per- and polyfluoroalkyl substances, endocrine-active compounds and microplastics, while examining the mechanisms and sustainability trade-offs that determine whether apparent removal represents transformation, retention or simple transfer between environmental compartments. Literature from 2010 to 18 July 2026 was synthesised alongside selected earlier methodological and foundational studies. The evidence indicates that contaminant behaviour is strongly compound-specific and governed by hydrophobicity, ionisation, persistence, plant traits, rhizosphere activity, hydraulic residence time, biofilm maturity and water chemistry. Mesocosm studies demonstrate substantial attenuation of some pharmaceuticals, endocrine-active compounds and pesticides, but persistent compounds such as carbamazepine and perfluoroalkyl acids are less consistently removed. PFAS studies show that plant uptake, sedimentation and sorption can attenuate aqueous concentrations without destroying terminal PFAS, creating a requirement for biomass and sediment management. Antibiotic studies show that bioaugmentation can increase parent-compound removal, but commonly use concentrations far above those found in receiving waters and provide little evidence on antibiotic-resistance genes. Microplastic evidence introduces a further sustainability concern because floating polymer components can become contaminant sources. Hybridisation with sorbents, immobilised microorganisms or bioelectrochemical systems can improve treatment, but also increases material, maintenance and end-of-life burdens. The field therefore requires mass-balance designs, transformation-product analysis, environmentally realistic exposures, long-term field validation and lifecycle-aware performance metrics before FTWs can be regarded as broadly reliable treatment barriers for emerging contaminants.