Emergent plants used in free water surface constructed wetlands: A review

•Macrophytes have important roles in free water surface constructed wetlands.•FWS CWs are used for treatment of various types of wastewaters.•Most common plant genera used in FWS CWs are Typha, Scirpus and Phragmites.

Constructed wetlands with free water surface (FWS CWs) have been used for many purposes worldwide. Emergent macrophytes play important roles in FWS CWs; they reduce wind speed and thus support sedimentation and prevent re-suspension, provide substrate for periphyton and bacteria, take up nutrients and in carbon-limited systems provide carbon for denitrification during biomass decomposition. It has been reported that treatment performance of planted FWS CWs is superior to unvegetated lagoons. However, treatment performance of FWS CWs could be affected by plant species used. The literature survey of 643 FWS CWs from 43 countries recorded 150 plant species and revealed that the most commonly used macrophyte genera were Typha, Scirpus (Schoenoplectus), Phragmites, Juncus and Eleocharis. In terms of species, most frequently used species were Typha latifolia, Phragmites australis, Typha angustifolia, Juncus effusus, Scirpus lacustris, Scirpus californicus and Phalaris arundinacea. In terms of continents, P. australis is the most frequent species in Europe and Asia, T. latifolia in North America, Cyperus papyrus in Africa, P. australis and Typha domingensis in Central/South Americas and Scirpus validus (S. tabernaemontani) in Oceania.