Effects of plant species in a horizontal subsurface flow constructedwetland – phytoremediation of treated urban wastewater withCyperus alternifolius L. and Typha latifolia L. in the West of Sicily (Italy)

Plant species carry out a series of important biological, chemical and physical processes within a con-structed wetland wastewater treatment system and make a significant contribution to wastewaterpurification. This paper compares two emergent macrophytes – Cyperus alternifolius L. and Typha latifolia L.– planted separately in a pilot horizontal subsurface flow system for the phytoremediation of treated urbanwastewater in the West of Sicily (Italy). The total surface area of the three units within the pilot system was99 m2. Six subunits were planted with two species and three subunits were left unplanted as the control.The main aim of the study was to demonstrate that, under identical hydraulic and design conditions, notonly the use but also the choice of plant species significantly influences wastewater treatment processeswith regard to all chemical, physical and microbiological parameters. The reedmace colonized a largersurface area and produced significantly higher yields of aboveground (3221 g m2/year) and belowground(4071 g m2/year) biomass than the umbrella sedge. Nitrogen content was also found on average to behigher in the reedmace-based treatments (40.6 g m2/year for aboveground and 62.7 g m2/year for below-ground parts). A good level of BOD5removal (72.4% for reedmace and 64.8% for umbrella sedge-basedtreatments) was obtained. Escherichia coli removal efficiency did not exceed 89.5%.