Groundwater Quality in a Rural Fractured Aquifer: Evidence of Physicochemical–Microbiological Decoupling in Drinking Water Safety Assessment

This exploratory baseline study examined whether this assumption holds in a rural fractured crystalline aquifer in the Monte Bonito district, within the Santa Bárbara Stream watershed (southern Brazil). Ten wells (shallow dug wells and semi-artesian boreholes) were sampled during a single baseline campaign conducted between September and October 2021, and physicochemical and microbiological parameters were compared against Brazilian drinking-water standards (Portaria GM/MS nº 888/2021).

Five of the ten wells exceeded at least one physicochemical threshold, most often iron, manganese, turbidity, or apparent color. In contrast, total coliforms were detected in all ten wells and Escherichia coli in nine, including a 35-m semi-artesian well that met all measured physicochemical criteria. Consequently, none of the ten wells met overall potability criteria once the microbiological domain was considered, even though half of the wells were physicochemically compliant.