Hydrochemical and microbiological assessment of groundwater from the weathered basement aquifer in Ibadan Metropolis, SW-Nigeria

A hydrogeochemical study was carried out on the shallow groundwater system of the weathered regolith aquifer within Ibadan Metropolis, with the objective of determining geochemical characteristics as well as identifying the influence of household activities on both chemical and microbiological quality status. Hydrochemical analyses of water samples from 50 shallow dug-wells revealed total dissolved solids of 54-1055 mg/L (ay. 373 mg/L) and dominance of Ca, Na and HCO3 as major ionic components, thereby suggesting a precipitation dominated low mineralized water system with limited residence time typical of a weathered crystalline bedrock setting. However, the total heterotrophic bacteria count (THBC) in the range of 20-3500 and coliform bacteria (E. coli) of 1-200 in some of the water samples alongside high NO3 concentration, is a clear indication of impacts of human waste inputs through in-house septic/soakaway pits.