Quantification and analysis of the viability of (oo)cysts of pathogenic protozoa in sewage sludge

Abstract

© 2018, Eduem - Editora da Universidade Estadual de Maringa. All rights reserved. This study aimed to quantify Giardia spp. cysts and Cryptosporidium spp. oocysts and infer their viability in sludge samples from two sewage treatment plants. The method used consisted of three successive centrifugations followed by immunofluorescence assay and staining with propidium iodide.Samples were 100% (14/14) positive for cysts and 57.1% (8/14) for oocysts, with higher concentrations and mean viability above 75%. The change in the treatment of activated sludge, from extended aeration to conventional system, caused no difference in the concentration and viability of (oo)cysts. For the use of sewage sludge, it is extremely important to consider the microbiological aspect of this byproduct that poses direct and indirect risks to public health as for its inadequate handling and use.