Abstract

 The physicochemical analysis and microbial load of polluted Alamuyo River in Ibadan, Nigeria and selected wells along its course were evaluated. Toxic effects of water samples obtained from upstream (A) and down stream (F) of the river were also evaluated using Allium cepa root assay. The result of the analysis revealed that the water sample contained toxic substances. However, almost all parameters evaluated were within the allowable limit of treated wastewater. High microbial load was observed in river water samples compared to the well water samples throughout the sampling periods with overall highest value observed at Late Rainy Season upstream water sample (LRS-A). MPN of faecal coliform showed that LDS-A, ERS-F and LRS from A – F were significantly different.Echerichia coli, Bacillus substillis, Staphylococcus aureus, Pseudomonas fragiiwere among the microbes observed in the samples. T-test analysis on A. ceparoot length showed that only 50% of LDS-A, LDS-F and LRS-A were significantly different from control (P < 0.05) though there were reduction in root length in all concentrations tested through out the sampling period except 5% ERSA, 10% ERSF and 10% LRSF. Microscopic evaluation of A. cepa cells showed decreasing number of dividing cells and mitotic indices were not dose dependent in most cases. Chromosome fragments, bridge, lag and disturbed spindle were the aberrations observed in this study. Our result showed that water samples from the river contained toxic substances and high microbial load, which have effects on the surrounding wells due to infiltration.

Key words: Toxicity, Allum cepa, aberration, allowable limits, evaluation, phytotoxic.

Abbreviation

Abbreviations: LDS, Late dry season; ERS, early rainy season; and LRS, late rainy season.