Assessment of the Effect of Refinery Effluent Discharge on the Water Quality of Ubeji River, Delta State Nigeria

Abstract

This study assessed the impact of refinery effluent discharge on the water quality of Ubeji River, Delta State, Nigeria. Water samples were collected over a six-month period from five points along the river (discharge point, upstream and downstream) and one control station. Physicochemical parameters (pH, temperature, TDS, turbidity, DO, BOD, COD, nutrients, THC) and heavy metals (Fe, Zn, Cu, Pb, Cd, Cr, Ni) were analyzed using standard methods. Results revealed that most parameters were within the permissible standard limits of the Federal Ministry of Environment (FMEnv), however, significant spatial variations (p<0.05) were observed. Dissolved oxygen at the discharge point (4.45 mg/L) fell below the FMEnv minimum limit of 5.0 mg/L, while BOD (4.62 mg/L) and COD (10.22 mg/L) indicated moderate organic pollution. Total hydrocarbon content (3.95 mg/L) and heavy metals were highest at the effluent entry point (discharge point) but declined downstream, though all remained below regulatory thresholds. Turbidity levels exceeded the FMEnv limit (5 NTU) across all stations. The Water Quality Index (WQI) categorized discharge point as poor, downstream section as good, while upstream section as excellent. Overall, refinery effluent has a measurable negative impact on Ubeji River, particularly on oxygen balance, organic load, and hydrocarbon levels, posing risks to aquatic life and dependent communities. The findings underscore the urgent need for stricter enforcement of effluent treatment standards, continuous monitoring, and sustainable management strategies to safeguard public health and ecological integrity.