Surface-Flow Constructed Treatment Wetlands for Pollutant Removal: Applications and Perspectives

I review the technology and application of free-water surface flow (FWS), macrophyte-dominated constructed treatment wetlands (CTWs) for pollutant removal. FWS-CTWs are used to remove a wide range of pollutants from various wastewaters. In FWS-CTWs, hydrologic conditions have a key influence on the biotic community, biogeochemical processes, and the fate of pollutants. Therefore, understanding the interactive effects of hydrology and biotic communities is critical to pollutant removal. In the past two decades, studies and applications of FWS-CTWs have increasingly focused on four wetland technologies: 1) tertiary treatment wetlands, 2) submerged aquatic vegetation (SAV) dominated systems, 3) FWS constructed wetlands for watershed management, and 4) hybrid systems. Managing FWS-CTWs, including adjustment of flow and water depth is crucial to the sustainability of effective treatment. Multiple functions and services of FWS-CTWs such as biological conservation and other ancillary benefits can be added while FWS-CTWs are applied to wastewater treatment. To reduce the acreage necessary for pollutant removal, coupling FWS-CTWs with other technologies has an application perspective for water quality improvement. Using FWS-CTWs is cost effective and environmentally sound for water sanitation, reuse, and conservation and supports sustainable resource management.