This research focused on hydrochemistry and sanitary risk assessment of domestic hand-dug wells in Ado-Ekiti, southwestern Nigeria with a view to improve/ensure the safety of the drinking water supply in the study area. To carry out the sanitary risk assessment, all the hazards and hazardous events that can affect the safety of water supply from the shallow wells through treatment and distribution to the consumers’ point of use were identified and evaluated. Subsequently, 30 water samples fairly spread over the catchment area were taken and analyzed for chemical constituents employing Atomic Absorption Spectrometer for the cations and ion chromatography for the anions. E-coli of another set of the 30 water samples were determined using standard method. Result of the sanitary survey revealed that 14 of the sampled wells were at high risk with 13 and 3 of them in intermediate and low risk respectively. The hydrochemistry of the groundwater revealed that most of the wells in the study area were at risk of contamination as indicated by the high chemical concentrations of NO3- (>50mg/L) and Cl-(>250mg/L) in 43% and 70% of the sampled water respectively. All other chemical parameters have concentrations within approved WHO standard for drinking water. E-coli were present in 90% (27out of 30 samples) of the water samples and this clearly support the sanitary survey of which 27 of the sampled well water fell into high to intermediate risk category. The study indicated that 90% of the wells in the study area are at risk of contamination. High concentrations of NO3- and Cl- from hydrochemical evaluation of the well water as well as presence of e-coli in 90% of the water indicated that the sources of pollution are from anthropogenic sources related to human and animal wastes at close proximity to wells. Safety of the water from the hand dug wells can be improved if health education is intensified in the area.
Keywords: Chemical Parameters, Contamination, E-Coli, Hazards and Hazardous Events, Sanitary Risk Assessment
