Seasonal Variations and Water Quality in Amazonia: A Comparative Study of Public Supply Systems in Oriximiná, Pará, Brazil

Introduction: Assessing the quality of water for human consumption is essential to ensure its suitability and mitigate health risks by preventing waterborne diseases. Objective: To evaluate the physicochemical and microbiological parameters of water supplied by two public systems in Oriximiná, Pará, Brazil, and to identify seasonal variations in these parameters during drought and flood periods. Methodology: The study compared two water supply systems: Companhia de Saneamento do Pará (Cosanpa) and Residencial Tia Ana. Water samples were collected monthly from January to December 2021 and analyzed for pH, apparent color, temperature, turbidity, chlorine, and coliforms following standardized procedures. Statistical analysis utilized Student's t-test and paired t-test with a significance level of 0.05. Results: The average temperature did not differ significantly between Cosanpa (22.5°C) and Residencial Tia Ana (22.3°C). Turbidity was higher in Cosanpa (1.56 NTU) compared to Residencial Tia Ana (0.48 NTU). Both systems had pH levels below the recommended range, reflecting the natural acidity of Amazonian waters. Apparent color was zero in Residencial Tia Ana and varied in Cosanpa. Free residual chlorine was detected only in Cosanpa (1.67 mg/L), indicating effective disinfection. Total coliforms were found in 8.33% of Cosanpa samples and 91.66% of Residencial Tia Ana samples. Conclusions: The study highlighted significant differences in water quality between the two systems, with Cosanpa exhibiting better quality due to adequate disinfection, while Residencial Tia Ana showed an urgent need for improvements in water treatment and disinfection. Keywords: Microbiological contamination; Disinfection; Physicochemical parameters; Water supply systems; Water treatment.