Performance of a Pilot-Scale Constructed Wetland and Medium-Term Effects of Treated Wastewater Irrigation of <i>Arundo donax</i> L. on Soil and Plant Parameters

On marginal lands in the Mediterranean basin, giant reed (Arundo donax L.) represents one of the most interesting perennial crops due to high levels of biomass production. Considering periodic water shortage during the summer months in this area, the reuse of treated wastewater (TWW) would seem to be a good opportunity for the growth of the species. The aim of this study was to assess the medium-term effects of irrigation using freshwater (FW) and TWW on soil characteristics and growth in giant reed plants. TWW was obtained from a pilot-scale horizontal subsurface flow constructed wetland system (HSSF CWs) with a total surface area of 100 m2. A split-plot design for a two-factor experiment was used with three replications. Medium-term TWW irrigation increased organic matter and plant nutrients in the soil; however, pH was not affected. Plants irrigated with TWW showed greater growth (+10.49% in height, +12.75% in stem diameter, +11.51% in above-ground biomass) than those irrigated with FW. The higher heating value of crop residues ranged between 16.83 (FW-irrigated plants) and 17.00 MJ kg−1 (TWW-irrigated plants). Results show that HSSF CWs produces TWW, which can be an alternative source of water for growing giant reed with high biomass performance