Design, implementation, and challenges of floating treatment wetlands for wastewater treatment: A review

Rapid population growth has significantly increased the demand for water and land and has contributed to surface water pollution and global warming. These issues can be addressed collectively through floating treatment wetlands (FTWs), which treat water bodies such as lakes, ponds, reservoirs, and stormwater systems without occupying land space. Constructed floating wetlands are a type of surface-flow wetland that generally consists of a floating platform supporting plants, with roots extending into the water. They are designed to treat various wastewaters like stormwater, sewage effluent, eutrophic lakes, streams, industrial wastewater, and tertiary wastewater from agri-food sources. The long fibrous roots either treat wastewater directly or indirectly by promoting microbial biofilm growth in the rhizosphere. With design improvements, FTWs have the potential to enhance water treatment, increase resilience to climate change, provide community benefits, and support biodiversity. Various software and analytical approaches can be used to design and predict the system's optimal treatment efficiency. The integration of technologies such as biofilm carriers, microbial fuel cells, and microbial consortia into FTWs is an emerging area of research. While FTW can reduce pollutant levels, it faces several challenges, including longer setup times, limited or uneven treatment, limited adaptability to seasonal shifts, and scalability and maintenance issues that must be addressed for large-scale use. This review examines FTW's design criteria, modelling tools, treatment mechanisms, obstacles to practical application, emerging innovations, and future innovations.