Microbiological composition of sludge generated in water treatment plants

Studies that focus on the microbiological composition of water treatment plants (WTP) sludge, as well as its pathogenicity, are extremely necessary, especially with regard to environmental regulations, where the microbiological characterization of WTP waste can encourage new policies related to its management. In Brazil, few studies address WTP sludge, which, in general, is classified as non-hazardous and non-inert waste, with the microbiological characterization of this material being little explored. This case study performed the microbiological characterization of sludge samples from two WTPs located in the state of São Paulo, before and after the centrifugation process. The determination of microbial density and morphology, Gram staining, and the identification of the presence of total and thermotolerant coliforms were performed with samples produced in two different years, in WTPs that used different coagulants (liquid aluminum sulfate or polyaluminum chloride and ferric chloride). Results were evaluated along with the physicochemical analysis of the composition of this waste. The presence of microalgae and protozoa in non-centrifuged WTP sludge and the presence of total and thermotolerant coliforms in WTP sludge before and after centrifugation are among the main results of this study.