Assessing the Quality of Surface Water for Direct Rural Water Supply: A Case Study of Osun River, Nigeria

Water is one of the most essential resources for life and living. Yet, many of our surface water bodies in Nigeria are under constant unabated attack of anthropogenic pollution. This study assessed the level of pollution of Osun River to determine the suitability of the river for domestic water supply. Samples from eight (8) different tributaries to Osun River were taken and analysed using standard procedures. The physical, chemical and biological parameters (TDS, Turbidity, Colour, Temperature, Chloride, Conductivity, Lead, Iron, Hardness, Nitrate, pH, Total Coliform , E. Coliform and Biological Oxygen Demand ) were compared with the Federal Environmental Protection Agency Standards and also subjected to statistical analysis (two way ANOVA and Correlation analysis). The Duncan Multiple Range Test (DMRT) was further used to explain the differences between the means. TDS, Turbidity, Colour, Temperature, Chloride, Conductivity, Lead, Iron, Hardness, Nitrate, pH were within permissible limits while the biological parameters indicate very high organic pollution. The highest Biological Oxygen Demand of 390mg/l, Total Coliforn Count of 330mg/l and Escherichia coli form count of 175mg/l were recorded for the IjebuJesha tributary. Statistical analysis showed significant difference between the physical and chemical parameters considered, but no difference between the parameters for each of the sampling points. The biological parameters showed significant difference for both the parameters and the sampling points since F>3.74 and P<2.76 and P<<0.05 for the sampling points. The correlation between the parameters for all the sampling points gave high correlation values which ranges between 0.5343 and 0.9972 as expected since the sampling points are all distant tributaries to a common source. Osun river has high level of organic pollution load and cannot be used directly without appropriate biological treatment.