Assessment of Physicochemical and Metal Characteristics of Effluent in Ebonyi State, Nigeria in Comparison with WHO Guidelines, Implications for Aquatic Ecosystem Health and Food Security

Industrial and domestic effluent discharges contribute significantly to surface and ground water pollution. Industrialisation in rapidly urbanizing regions of Sub-Saharan Africa often impacts our environment, leading to severe aquatic degradation. This study presents a comprehensive physicochemical, metal and toxicological characterization of industrial effluents within the Abakaliki metropolis, Ebonyi State, Nigeria. Twenty-nine representative samples were collected from strategic discharge points, including Royal Salt processing area which doubles as lead and zinc mining region, Abattoirs, Building material market area, Iyiudele River and Municipal drainage canals. Analysis was conducted following APHA and ASTM standard protocols for eighteen parameters, including heavy metal speciation through spectrophotometry. Results indicated a critical state of pollution, with several parameters significantly exceeding WHO (2023) and SON permissible limits. Notably, Arsenate (As) and Lead (Pb) exhibited mean concentrations of 0.07 mg/L and 0.105 mg/L respectively, representing a high percentage exceedance of safety thresholds. Organic loading was equally severe, with Biochemical Oxygen Demand (BOD₅) averaging 88.5 mg/L (CF = 2.95) and Dissolved Oxygen (DO) levels dropping to a hypoxic mean of 1.85 mg/L. Furthermore, extreme nutrient enrichment was observed, with Total Phosphate (5.29 mg/L) exceeding the limit by over ten-fold, signaling a high risk for irreversible eutrophication in receiving water bodies like the Iyiokwu River. Statistical analysis (ANOVA, p < 0.05) confirmed significant spatial variation in contaminant plumes, specifically linking Royal salt processing to metal toxicity and abattoir discharge to organic hypoxia. The study concludes that the uncontrolled discharge of these untreated effluents poses an immediate threat to the regional "One Health" framework, necessitating urgent bio-remediation strategies—such as phytoremediation and low-cost adsorption treatment methods alongside stricter enforcement of NESREA discharge permits. These findings provide a baseline for future longitudinal studies on the biomagnification of neurotoxic metals within the local food chain.