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

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.

Ten major rivers were sampled between April and August, 2021. The pH, temperature, total al- kalinity, 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.

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 differenc- es 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.

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