Abstract

Samples of water from two rivers (River Ona and River Alaro) in Oluyole Industrial Estate, Ibadan, Nigeria were analysed to evaluate the impact of industrial discharges on the surface water quality. The results obtained indicated that most of the parameters analysed (pH, total hardness, sulphate, chloride, nitrate and dissolved solids) were lower than the World Health Organisation (WHO) maximum permissible limit for drinking water. However, the levels of nitrate, chloride, total phosphorus, total solids and oil and grease were higher in the industrial zones than those found in the upstream of both rivers. These ranged between 3.00 – 8.55, 7.48 – 11.78, 2.14 – 3.57, 260 – 520 mg/l and 381.20 – 430.80 mg/l, respectively. Nitrate and total phosphorus which are essential nutrients for plants were the most accumulated in both rivers. The gross organic pollution indicators monitored (chemical oxygen demand and oil and grease) revealed that River Alaro was more polluted than River Ona. It was established from the results of this study that industrial discharges had negative impact on the surface water qualities of both rivers. Hence, extraction of water from both rivers for domestic and agricultural purposes requires some forms of physical and chemical treatment.

Key words: River Ona, River Alaro, industrial discharges, surface water quality.

Abbreviation

Abbreviations: MEHHs, Modern environmental health hazards; COD, chemical oxygen demand; AF, accumulation factor; DO, dissolved oxygen.