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

Abstract

Plant species carry out a series of important biological, chemical and physical processes within a constructed wetland wastewater treatment system and make a significant contribution to wastewater purification. 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 urban wastewater in the West of Sicily (Italy). The total surface area of the three units within the pilot system was 99m2. 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, not only the use but also the choice of plant species significantly influences wastewater treatment processes with regard to all chemical, physical and microbiological parameters. The reedmace colonized a larger surface area and produced significantly higher yields of aboveground (3221gm2/year) and belowground (4071gm2/year) biomass than the umbrella sedge. Nitrogen content was also found on average to be higher in the reedmace-based treatments (40.6gm2/year for aboveground and 62.7gm2/year for belowground parts). A good level of BOD5 removal (72.4% for reedmace and 64.8% for umbrella sedge-based treatments) was obtained. Escherichia coli removal efficiency did not exceed 89.5%.