Physicochemical Changes in the Quality of Surface Water due to Sewage Discharge in Ibadan, South-Western Nigeria

Sewage discharge is known to degrade the quality of receiving water bodies. This study assesses the impact of black water discharge on the physico-chemical parameters of River Zik in the University of Ibadan. Water samples were collected from five sampling sites along the stream located at progressive distances from the discharge point. Sampling was done three times over a period of three months (May to July 2012). The physico-chemical parameters tested were- pH, Biochemical Oxygen Demand (BOD5), Dissolved Oxygen (DO), Electrical Conductivity (EC), Total Suspended Solids (TSS) and Nitrate. The overall mean values of the measured parameters were as follows- BOD5 (381.1 mg/L); DO (3.9 mg/L); SS (1825.4 mg/L); pH (6.1); EC (618.5 ?s/cm) and Nitrates (59.8 mg/L). The highest concentrations of BOD5, SS, EC and Nitrates were obtained at the point of sewage discharge into the stream. One-way ANOVA showed significant deviation from WHO standards for BOD5, SS, DO, EC and Nitrates (p < 0.05). This study showed that sewage discharge into River Zik have seriously contributed to the pollution of the stream to levels which pose health and environmental hazards to those using it downstream for domestic and agricultural purposes. This environmental hazards has been attributed to the little or near none existence of regulatory bodies responsible for regulating the strenght of black water discharge into sewers and/or recieving water bodies.