Assessment of Microbial and Physicochemical Characteristics of Groundwater in Selected Local Government Areas of Oyo State, Southwest Nigeria

Negative impacts of contaminated groundwater on human health are chronic and are very difficult to detect. This study assessed the extents of groundwater contaminations based on the level of microbial and physicochemical characteristics in selected local government areas (LGAs) of Oyo-State, Southwestern Nigeria. Groundwater samples were collected from 10 wells per each LGA (50 wells in total), in-situ measurement of physicochemical parameters namely pH, temperature, electrical conductivity (EC) among others and microbial analyses were also carried out using standard laboratory procedures through isolation and identification of microbes, confirmation of isolates and protozoan analysis. The acquired data were subjected to Analysis of variance (ANOVA) and Duncan multiple range test (DMRT) to evaluate their level of significance. The results revealed that the mean distribution of the physicochemical parameters ranged from 4.7±0.15−8.9±0.21b; 26.7℃±3.06c−30.9℃±1.63b; 119±0.58a−599.7±9.07g (mg/l); 15.6±0.51a−82±2.0f (µs/cm) respectively for pH, temperature, TDS, EC. The results of the microbial analyses revealed that most of the water samples were contaminated with a total number of ten (10) isolates namely Citrobacter freundii, Shigella dysenteriae, Enterobacter aerogenes, Escherichia coli, Proteus vulgaris, Klebsiella pneumoniae, Salmonella typhi, Bacillus subtilis, Pseudomonas aeruginosa and Vibrio cholerae. In terms of maximum exhibited bacteria loads, the most contaminated area is Oja-Oba (OJB) with 4.0 × 102 cfu/ml and the least contaminated area is Iwo-road (IWR) with 2.0 × 102 cfu/ml while in terms of compliance level, the most contaminated area is OJB and the least contaminated area is Apata (APT) with 10% and 60% compliance levels. Therefore, the investigated areas, most particular OJB groundwater are hereby recommended for comprehensive treatment.