Existe segurança microbiológica na portaria de potabilidade GM/MS 888/2021 nas condições da região semiárida do Brasil?

Abstract

The study was based on the monitoring of two water treatment plants, of different sizes and supplied by the reservoir Epitácio Pessoa - PB, in order to assess whether there is microbiological safety in what advocates the potability standards of Ordinance of GM/MS nº 888 /21 in surface water treatments in the Brazilian semi-arid region. Water collections for analyzes were carried out weekly, during the sampling period between June 2022 and November 2022, comprising 22 (twenty-two) samples for each of the ETAs. The parameters of turbidity, apparent color, pH, temperature, residual chlorine, spores of aerobic bacteria, total coliforms, E. coli and the estimate of Giardia inactivation from the USEPA model were analyzed throughout the water treatment steps. Raw water showed low turbidity values, high concentrations of EBA and absence of E. coli in all analyzed samples. The water clarification step in both ETAs was ineffective, showing an increase in spore concentration and slight removal of turbidity. The filtration stage was responsible for the greater EBA treatment efficiency, both at ETA Gravatá and ETA Cariri, reaching average values of removal around 1 log. When comparing the efficiency of turbidity and EBA removal in the clarification + filtration steps, it is observed that the efficiencies, instead of increasing, cancel out due to the inefficiency in the clarification step, overloading the removal only in the filtration step. The results of inactivation of Giardia were also not satisfactory, with averages of removal below 0.5 log, this fact may be associated with the Ct (residual disinfectant x contact time) that were below the recommended by the ordinance, making the inactivation process unfeasible of microorganisms. Due to the operational and structural problems of the ETAs, it was not possible to meet the potability standards recommended by the current legislation, in relation to most of the evaluated parameters.