Growth of Arundo donax L. and Cyperus alternifolius L. in a horizontal subsurface flow constructed wetland using pre-treated urban wastewater - a case study in Sicily (Italy)

Abstract

Constructed wetland systems for wastewater treatment represent an excellent opportunity for the recovery of water resources in those areas subject to prolonged periods of water shortage. This paper presents a study of the efficiency of a pilot horizontal subsurface flow system using pre-treated urban wastewater from a small town in the West of Sicily. The pilot system had a total surface area of 100 m2 with two units. Unit A was planted with Arundo donax L. and unit B with Cyperus alternifolius L. The HLR was 10 cm d-1. The main objectives of research were to evaluate the growth and biomass yield of two macrophytes and determine the removal efficiency of physical-chemical and microbiological parameters. The results showed excellent organic pollutant removal (BOD5 70-72%, COD 61-67%) whilst macronutrient removal was found to be lower (TKN 47-50%, TP 43-45%). Pathogen load removal was found to be approximately 90% but Escherichia coli concentrations at outflow were not within Italian legislative limits. Giant reed showed higher nitrogen content in the biomass (average 28.9 ± 1.8 g m-2 year-1 for aboveground and 63.8 ± 1.8 g m-2 year-1 for belowground parts) than umbrella sedge. The treated wastewater was used to irrigate parkland areas.