DESINFECCIÓN DE AGUAS RESIDUALES EN TRES SISTEMAS DE HUMEDALES CONSTRUIDOS HÍBRIDOS

Three pilot-scale hybrid constructed wetlands systems were evaluated in order to compare their efficiency in the removal of total coliforms and Escherichia coli. The first system consisted on horizontal subsurface flow constructed wetlands (HSSF-CW) followed by stabilization ponds (SP), the second one by HSSF-CW followed by vertical subsurface-flow constructed wetland (VSSF-CW), and the third one by VSSF-CW followed by HSSF-CW. The systems were evaluated in duplicate for one year of operation, four months of stabilization and eight months of monitoring. The HSSF-CW:VSSF-CW and VSSF-CW:HSSF-CW systems were the most effective for the removal of both indicator organisms. In these systems, E coli was reduced in 3-4 log units and average concentrations of 1000 ± 300 and 210 ± 60 MPN/100ml, respectively, were reached. Global removal efficiencies were 99.93% and 99.99%, respectively. These results show that it is possible to achieve natural wastewater disinfection by using hybrid wetland systems with two well-selected stages.