Assessment of Water Quality and Heavy Metal Pollution in Egbewa and Awemu Rivers Relative to WHO Standards

Abstract

This study evaluates the physicochemical parameters and heavy metal concentrations in the Egbewa and Awemu Rivers, located in southeastern Nigeria, using water samples collected from four spatial points: upstream (A), midstream (B), downstream (C), and estuary (D). Key parameters including dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), electrical conductivity (EC), pH, total hardness, chloride, total dissolved solids (TDS), turbidity, phosphate, nitrate, cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn) were analyzed and compared against World Health Organization (WHO) guidelines. Results indicate that Egbewa River exhibits stable water quality with DO levels averaging 5.46 mg/L (within WHO limits for aquatic life) and low organic pollution (BOD: 0.81 mg/L; COD: 3.16 mg/L), but elevated Cd (0.11 mg/L) and Pb (0.50 mg/L) concentrations exceed safe thresholds, posing health risks.