Reuse of sewage treated effluent in agricultural practices: An alarming presence of Giardia spp. cysts

It was evaluated the removal efficiencies of Giardia spp. cysts and helminth eggs by a simplified system of wastewater treatment. The treated effluent was checked to be reused in agricultural practices. The system was composed by anaerobic filter and intermittent sand filter. Final effluent concentration was: COD of 52 ± 24 mg L−1, TSS of 17 ± 20 mg L−1 and low turbidity values (3 ± 4 UT). The anaerobic filter could remove 99.7 ± 28.7% of estimated cysts concentration in the raw sewage. The sand filter removed 38.0 ± 31.6% of Giardia spp. cysts from the anaerobic effluent, inducing the total efficiency of the system to 99.8%. The system could also remove 100% of helminth eggs. However, we also identified 93 ± 92 cysts L−1 in the final effluent. Thus, there is a necessity to further study these decentralized systems in order to prevent the spread of infectious parasites forms in agricultural practices.