Hydrogeological potential and qualitative assessment of groundwater from the Ajali Sandstone at Ninth mile area, southeastern Nigeria

Investigations were conducted to determine the geo-electric properties, aquifer potential and quality of groundwater samples of the Ajali Sandstone Formation at Ninth mile area, Nigeria. Results reveal that the formation has 4–6 geo-electric layers, with the fifth recording hydraulic conductivity, transmissivity and transverse resistance values that suggested a general high yield to boreholes. The aquifer longitudinal conductance analysis indicates poor aquifer protective capacity, thus, high risk of contamination by effluents from the heavy industries within the area. Qualitative analysis shows major ionic concentrations, in the order: Na+ > K+ > Ca2+ > Mg2+ > Fe2+ > HCO3− > Cl− > SO42− > NO3−, that satisfy all permissible limits for drinking purpose. All tested samples have heavy metals, except Pb2+, and also fall within acceptable limits. High amount of Pb2+ originated most probably from improper disposal of ‘leaded’ petroleum products or leaching of lead from metal casing used in the well development. That the water samples satisfied almost all limits for drinking purpose despite the poor aquifer protective capacity and high industrialization may imply that the wastewater received fairly adequate treatments before discharge. Caution should, however, be applied in dealing with factors that give rise to lead contamination and in the water usage.