Assessment of well water pollution by sewage contaminants: A case study of Akure South, Ondo State, Nigeria

Abstract

This study investigated the extent of well water contamination in dry and rainy seasons through infiltration of coliform bacteria from sewage pits in their proximity in Akure. Total and Faecal coliform counts of twenty household wells were investigated between the months of March and July with respect to proximity of wells to sewage pits, orientation of wells to sewage pits, and other well characteristics. All wells studied were assessed to be vulnerable to contamination with observable differences in characteristics, physicochemical parameters, total coliform counts and faecal coliform counts. Asides pH which was higher in the dry season, all other parameters had lower values in the dry season. At an average distance of 17.6 m from the sewage pits, all well water sampled had greater coliform counts than the WHO recommended level for drinking water (< 1 cfu/mL). Correlations between coliform counts of water samples and the distances of the wells to sewage pits was positive and not significant for both total and faecal coliform in dry season, while it was negative and significant for both total and faecal coliform in the rainy season. Topography, and distance between wells and sewage pits were prominent factors responsible for well water contamination. Amounts of coliforms found in wells were significantly affected by seasonal variation. It is thus suggested that wells be sited up-gradient and at safer distances away from sanitary systems in the ultimate bid to reduce groundwater pollution and the occurrence of water borne diseases.