Impact of Effluent of an Industrial Estate on Oruku River in Southwestern Nigeria

The impact of industrial effluent on the Oruku River in southwestern region of Nigeria was investigated. Surface water, sediment, ground water and industrial effluent samples were obtained bimonthly for 18 months (March 2005 to September 2006). Effluent characteristics varied widely with averages of DO (4.25±1.3 mg/L), BOD (27.5±43 mg/L), Pb (0.41±0.26 mg/L), Cr (0.26±0.48 mg/L) and Ni (0.19±0.14 mg/L). Average metal concentrations of surface water at effluent discharge point were: Pb (0.065±0.065 mg/L), Cd (0.012±0.023 mg/L), Cr (0.11±0.23mg/L) and Ni (0.114±0.075mg/L). Values decreased to Pb (0.018±0.035 mg/L), Cd (0.004±0.003 mg/L), Cr (0.036±0.081mg/L) and Ni (0.025±0.023mg/L) few kilometres downstream. Contaminant levels were strongly correlated (r = 0.997) between surface water and bottom sediments. Ground water quality was within the permissible limits of the FMENV and WHO. The industrial effluent and surface water were evidently polluted with heavy metals and trace organics. Surface water contamination was related to the discharge of untreated industrial effluent. These could be of health and environmental hazard to settlements along its banks. There is need for regular monitoring of effluent, surface water and ground water quality to comply with regulatory standards.