Reuse of constructed wetland effluents for irrigation of energy crops

The competition for freshwater between agricultural, industrial, and civil uses has greatly increased in Mediterranean basin characterized by prolonged dry seasons. The aim of this study was to evaluate biomass production of promising "no-food" energy crops, Vetiveria zizanoides (L.) Nash, Miscanthus x giganteus Greef et Deu. and Arundo donax (L.), irrigated with low quality water at different ETc restitutions (0%, 50 and 100%). Two Horizontal SubSurface Flow constructed wetland beds (H-SSF1 and H-SSF2), with different operation life (12 and 6 years), were used to treat secondary municipal wastewaters for crops irrigation. Water chemical, physical and microbiological parameter as well as plant bio-agronomic characters were evaluated. The results confirm the high reliability of CWs for tertiary wastewater treatment given that the H-SSF1 treatment capacity remained largely unchanged after twelve years of operation. The average aboveground dry matter productions were 7 t ha-1 for Vetiveria zizanoides, 24 t ha-1 for Myscanthus x giganteus and 50 t ha-1 for Arundo donax. These results highlight attractive biomass yield and an interesting crop energy capability by using treated wastewater for irrigation.