Environmental impacts of an unlined municipal solid waste landfill on groundwater and surface water quality in Ibadan, Nigeria

Environmental and public health concerns grow on the interaction of municipal solid waste (MSW) leachates from unlined waste disposal sites with aquifers in many developing countries. This study investigated the environmental pollution impacts of an unlined MSW landfill at Ajakanga area, Ibadan, southwest Nigeria. Analytical studies indicated that the concentrations of NO3-, SO42-, PO43-, NH4-, Cl-, Na, Fe, Mn, Cr, and Mo in the leachate samples exceeded the WHO wastewater discharge limits. Hydrochemical parameters of the groundwater and surface water were within WHO allowable thresholds, except for EC, TDS, Fe, Mn, and Pb in the groundwater and Pb, Cd, and Cu in the surface water, indicating major geogenic and minor MSW leachate impacts on the groundwater and surface water chemistry. Bacteria found in the leachate include Enterobacter cloacae (16.67%), Pseudomonas spp. (14.28%) and Bacillus spp. (9.52%). The geoelectrical imaging data indicated substratum leachate infiltration greater than 10 m deep, which is consistent with the low resistivity values of the topsoil-weathered basement layers. The health risk assessment showed high hazardous index values, indicating health risks of Mn, Cd and Pb in the surface water for the residents around Ajakanga landfill. Hydrochemical data indicated greater impact of the MSW leachates on the surface water than the groundwater, while geophysical data showed greater propensity of the surrounding aquifer to leachate interaction through fractured basement zone with increasing abstraction. Waste site closure and hydrochemical monitoring are suggested measures to mitigate environmental pollution in the study area.