Spatial Distribution and Hydrogeochemical Factors Influencing the Occurrence of Total coliform and E. coli Bacteria in Groundwater in a Hyperarid Area, Ad-Dawadmi, Saudi Arabia

Coliforms (FB) posing population health risks in groundwater (GW) have been identified for decades, with recent studies assessing how hydrogeological and non-hydrogeological parameters correlate with their presence. This study focused on explaining the physicochemical and hydrological factors influencing the presence of fecal contamination in the GW system of Ad-Dawadmi, KSA, a hyperarid area facing a prolonged drought. It was designed and implemented by sampling 47 working wells and their laboratory analysis. The data analyses indicated that the salinity exhibited a purification effect such that at levels higher than 3500 and 6000 mg/L, no E. coli and total coliform (TC) were detected. Heavy metals, especially copper, showed strong, hygienic effects at 195 and 300 µg/L thresholds for E. coli and TC, respectively, while those of Fe were at 1200 and 2000 µg/L. Nitrates, dissolved organic carbon (DOC), and dissolved oxygen (DO) showed a quasi-random interrelationship with FB. The occurrence of FB in boreholes up to 52 m below ground level (BGL) challenges the single water resource in the region. Integrating various analyses help constrain and provide multiple lines of evidence for the inferred remarks. This work presented some methodological aspects for understanding the effects of the physicochemical and hydrogeological factors on FB that may better protect water quality and improve human health outcomes.