Estimation and evaluation of the risks of protozoan infection related to the water produced by a treatment plant in southern Brazil.

The main objective of this study was to estimate the risk of giardia and cryptosporidium infection through ingestion of the water produced by a treatment plant located in southern Brazil, between the years 2015 and 2021. The protozoan removal values ​​were obtained through two different approaches and the annual infection risks were estimated by the Quantitative Microbiological Risk Assessment Methodology (QMRA). Although the collected raw water showed a higher concentration of giardia cysts than cryptosporidium oocysts, the annual risk values ​​were significantly higher for cryptosporidium infection. The choice of the type of approach to estimate the removal of protozoa had a great impact on the magnitude of the infection risk values ​​obtained. In general, the water treated by the studied plant presented infection risk values ​​lower than or very close to the annual risk value considered tolerable by the World Health Organization (WHO). However, it was concluded that the conventional requirements present in norms and legislation, such as in Brazilian legislation, are not sufficient to guarantee the microbiological safety of drinking water.