Water Quality Assessment of Surface Water, Groundwater, and Wastewater in Bangui, Central African Republic: Physicochemical Parameters, Trace Metal Distribution and Microbial Contamination

Rapid urbanization and inadequate sanitation infrastructure threaten water security in many sub-Saharan African cities. This study aimed to provide an integrated assessment of groundwater, surface water, and wastewater quality in Bangui by characterizing physicochemical parameters, trace metals, and microbiological indicators, and by identifying potential contamination sources and pathways among these water compartments. A total of 28 water samples were collected from groundwater, surface water, and wastewater sites. Physicochemical parameters, major ions, trace metals, and microbiological indicators were analyzed using standardized methods, including ion chromatography, ICP-OES, ICP-MS, and membrane filtration. Results revealed a clear contamination gradient. Wastewater showed the highest electrical conductivity, turbidity, chloride concentrations, and microbial loads, reaching 2.41 × 106 CFU/100 mL for total coliforms and 1.93 × 106 CFU/100 mL for fecal coliforms. Groundwater exhibited high nitrite levels and low dissolved oxygen, indicating vulnerability to sewage infiltration. Surface waters were characterized by high turbidity and widespread fecal contamination despite relatively good oxygenation. In contrast, trace metal concentrations generally remained below World Health Organization guideline values. Geochemical analyses identified distinct elemental signatures for each water type. Microbiological contamination emerged as the dominant water quality concern. High fecal coliform/fecal streptococci ratios (13.08-22.16) indicated predominantly human-derived pollution linked to untreated wastewater and inadequate sanitation systems. The association between elevated nitrite concentrations and fecal indicators suggests active contamination pathways connecting wastewater, surface water, and shallow aquifers. These findings highlight the urgent need for improved wastewater management, groundwater protection, and long-term monitoring to ensure sustainable urban water security in Bangui.