Heavy Metal Speciation, Microbial Study and Physicochemical Properties of Some Groundwaters: A Case Study

Abstract

This study determined the physicochemical parameters, microbial properties and heavy metal speciation of groundwater in major towns of Ife North Local Government, Area of Osun State, Nigeria, with a view to evaluating the safety of groundwater. Water samples were collected during the dry season (December, 2015 to February, 2016) and wet season (May to July, 2016). A total of 72 samples were collected for the 6 months. Physicochemical parameters were determined in situ while total coliform count was done by membrane filtration techniques. The sequential extraction procedure was used to fractionate the metals (As, Pb, Cd, Cr, Cu, Mn, Ni and Zn) in the water samples. The concentrations of the metals were quantitatively determined using Atomic Absorption Spectrophotometer (AAS, PG 990 Series). The results of the physicochemical parameters of water showed that the pH (6.22–9.93), electrical conductivity (126.02–606.65 µs cm−1), total dissolved solids (78.37–705.31 mg L−1), oxidation reduction potential (303.44–330.17 mV) and temperature (25.83–28.93 °C) were within the limit stipulated for drinking and domestic water. The bacterial flora identified includes Escherichia coli, Yersinra spp, Entrerbacter spp, Citrobacter spp, Seirantia spp, Klebsella spp and Rhebrella spp. The metal speciation revealed free metal ions had the highest concentration with the order free metal ions > suspended particles > bound to organic substances. The study concluded that the groundwaters of the studied area were polluted with microorganisms and the investigated heavy metal, require treatment and monitoring to safeguard human health.