Reuse of constructed wetland effluents for irrigation of energy crops

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.), irrigatedwith low quality water at different evapotranspiration restitutions. Two horizontal subsurface flow(H-SSF) constructed wetland (CW) beds, with different operation life (12 and 6 years), were used totreat secondary municipal wastewaters for crops irrigation. Water chemical, physical andmicrobiological parameters as well as plant bio-agronomic characters were evaluated. The resultsconfirm the high reliability of CWs for tertiary wastewater treatment given that the H-SSF1 treatmentcapacity remained largely unchanged after 12 years of operation. Average TSS, COD and TN removalfor CWs were about 68, 58 and 71%, respectively. The Escherichia coli removal was satisfactory,about 3.3 log unit for both CW beds on average, but cautions should be taken as this parameter didnot achieve the restrictive Italian law limits for wastewater reuse. The average aboveground drymatter productions were 7 t ha1 for Vetiveria zizanoides, 24 t ha1 for Myscanthus x giganteus and50 t ha1 for Arundo donax. These results highlight attractive biomass yield by using treatedwastewater for irrigation with a complete restitution of evapotranspiration losses.