Pollution Assessment of Shallow Groundwater of Urban Area of Part of Southwestern Nigeria

Abstract

Water samples were collected from thirty hand – dug wells around Oyo township for bacterial and trace elements assessment. Total bacteria and coliform counts were performed using colony count and multiple tube technique and the pure culture was subjected to biochemical and sugar fermentation. Coliform count was estimated using Most Probable Number (MPN) method, while atomic absorption spectrophotometer (AAS) was used for the analyses of iron (Fe), lead (Pb), Zinc (Zn), Copper (Cu) and Cadmium (Cd) in the water samples. The total bacterial count (TBC) was very high as some were too numerous to be estimated. The MPN of the coliform bacteria was between 2 and 6 indicating faecal contamination in all the sampled hand-dug wells. Based on morphological, biochemical and TSI methods, the isolated bacteria from the water samples were identified to belong to two genera; Escherichia and Citrobacter. For trace element concentration (mg/L), the groundwater is uncontaminated with Zn, Cu and Cd but Fe and Pb occurred above the recommended limits in drinking water in many areas. Therefore, the dependent of rural dwellers on shallow groundwater should be placed under close monitoring so as to forestall outbreak of infection in the society. This is because the presence of coliform bacteria especially Escherichia coli is an indication of recent fecal or sewage contamination and presence of iron and lead above recommended levels is most likely from anthropogenic source.