Evaluation of the physicochemical properties and bacterial loads of selected rivers in Ondo State, Nigeria.

Background and objectives: Water is crucial to human existence but may be contaminated with microorganisms, thus making it unfit for consumption. This study aimed to evaluate the physicochemical properties and bacterial loads of selected river waters in Ondo State, Nigeria.

Materials and methods: Ten major rivers were sampled between April and August, 2021. The pH, temperature, total alkalinity, colour, turbidity, electrical conductivity, dissolved oxygen, ammonium, aluminium, organic matters, nitrate levels including the microbial loads were determined according to standard procedures. Confirmation of identified isolates was achieved by API 20E and API 20NE.

Results: The turbidity, colour, conductivity, ammonium, and aluminium ranged from 4.3 to 15.2 NTU, 4 to 20 NTU, 123.5 to 580.2 mgL^-1, 0 to 3.5 mgL^-1, and 0.05 to 1.7, respectively. Most physicochemical parameters showed no significant differences from the WHO permissible limits for drinking water (p > 0.05). The total viable bacterial count in the rivers ranged from 1.5 × 10⁵ to 6.3 × 10⁵ CFUmL^-1, while the total coliform count ranged from 1.3 × 10³ to 4.8 × 10³ CFUmL^-1. The predominant bacteria were Escherichia coli and Pseudomonas aeruginosa.

Conclusion: This study revealed that the physiochemical properties of the waters were majorly within the WHO permissible standards but with significantly higher bacterial loads.