Sanitary aspects, evidence of microplastics and seasonality interference in freshwater from shallow wells in Presidente Médici city - Rondônia state, Brazil

This study assessed the water quality of 10 shallow wells in Presidente Médici city, quantifying total and thermotolerant coliforms, as well as microplastic abundance. All wells exhibited total coliform levels exceeding the limits established by Ordinance No. 888/2021, indicating a significant public health risk. Microplastics were detected in 60% of the samples, with higher concentrations during the rainy season. Transparent and blue fibers were more abundant during this period, suggesting influence from urban effluents. In the dry season, black fibers and fragments predominated, possibly related to agricultural activities. The results highlight the urgent need for water treatment in these wells, such as filtration and chlorination, to ensure safe consumption. The research suggests that surface runoff contaminated by urban and agricultural effluents may have contributed to the pollution of the shallow wells. The waters of the wells analyzed did not meet the standards of current legislation for total and thermotolerant coliform parameters. Seasonality affected the values of both groups of microorganisms, so that they were higher during the rainy season. These waters need to be treated beforehand, such as filtration, boiling or chlorination, before consumption. Microplastics were present in 60% of the wells studied, demonstrating the variation according to seasonality.