Abstract

Contamination of surface waters by human activities remains a major public health concern, particularly in developing Countries. This study evaluated the bacteriological and physicochemical quality of water samples from a sand mining site in Ox-Bow Lake in Yenagoa, Bayelsa State, Nigeria. Water samples were collected at monthly intervals for a period of ten calendar months (August 2023 to May, 2024), covering both the dry and wet seasons and analyzed using standard techniques. Results revealed, Total heterotrophic bacteria counts ranged from 6.1×10⁵ –11.8×10⁵CFU/ml; total coliforms from 2.0×10⁴–20.2×10⁴ CFU/ml, total fecal coliform from 2.8×10⁴–14.2×10⁴ CFU/ml; Salmonella–Shigella from 1.4×10⁴–3.7×10⁴ CFU/ml,; and Vibriods ranged from 0.5×10⁴–2.9×10⁴ CFU/ml while Pseudomonads were absent. Seasonal variations showed microbial peaks in both dry and wet periods, driven by runoff and dredging activities. Potential pathogens identified included Vibrio cholerae, Salmonella typhi, Klebsiella pneumoniae, and Chromobacterium violaceum. Analysis revealed acidic pH range (5.37–5.47), low conductivity (32.74–37.94µS/cm), and poor mineralization. Dissolved oxygen was relatively high (8.57–9.57mg/L), but elevated biological oxygen demand (4.56–5.56mg/L), chemical oxygen demand (74.81–78.81mg/L), and phosphate concentrations (1.43–1.53mg/L) indicated significant organic and chemical pollution. The range of heavy metal concentration were; lead (2.101–2.234mg/L), iron (28.931–29.931mg/L), cadmium (2.672–3.772mg/L), and chromium (1.881–2.681mg/L). Total petroleum hydrocarbons ranged from 35.2811 to 39.19146µg/mL. Generally, the ranges of heavy metals and TPH in the control were far lower. These results show that the water samples were contaminated with potential pathogens known to cause disease. Additionally, the physicochemical characteristics of the water samples indicate substantial organic pollution. Heavy metals, including Pb, Fe, Cd, and Cr, were found at concentrations above safe limits, and the detection of total petroleum hydrocarbons showed the level of contamination, all raising health concerns. These findings highlight an urgent need for the monitoring of sand mining activities to safeguard the ecological health of Ox-Bow Lake.