Assessment of the quality of quaternary groundwater under the influence of anthropogenic activities in the low-income neighbourhoods of the Treichville municipality (Abidjan, Côte d’Ivoire)

Abstract

This study aims to assess the groundwater quality and the origin of water mineralization in an environment with high anthropogenic pressure in the municipality of Treichville. Twenty-one water samples were analysed to determine the quality. Kruskal–Wallis nonparametric test, Mann–Whitney test, Kohonen algorithm, and water table building were used to determine the factors influencing the mineralization. The results showed that the well’s water contains chemical and bacteriological elements whose concentrations are higher than the standards authorized by the World Health Organization (WHO). Thus, high levels of nitrate (peak = 173.1 mg L−1), phosphate (peak = 1.03 mg L−1), lead (peak = 2.987 mg L−1), and Escherichia coli (peak = 2.31 × 105 UFC 100 mL−1) were obtained in these waters. So, the groundwater is not suitable for human consumption. The most mineralized waters are found in the areas near the Ebrie Lagoon and extend in the direction including the low-income neighbourhoods of Biafra, Nanan Yamousso and Appolo. Pollutant transfer is continuous in the study area and comes from surface sewage, latrines, sewage disposal systems, well water collection materials, and the Ebrie Lagoon. Indeed, the pollutants leave Biafra neighbourhoods where water is heavily polluted and the pollution is amplified by the presence of septic tanks and latrines located on the line of groundwater flow. The main factors influencing water quality are the lagoon water intrusion, the advection mechanism linked to the infiltration of surface water and the lateral migration of pollutants from septic tanks and latrines, and mechanism of dissolution of the clay component of the clayey–sandy layers.