HYDROLOGICAL INVESTIGATION OF A MUNICIPAL SOLID WASTE DUMPSITE IN IYOWA, BENIN CITY, EDO STATE.

This study investigated the hydrogeological evaluation of borehole water contamination near a solid waste dumpsite in Iyowa, Benin City, Nigeria. The aim was to assess how dumpsite leachate affects groundwater quality by examining physicochemical, microbiological, and heavy metal parameters. Five borehole samples were collected at varying elevations and distances around the dumpsite (coordinates: 6°27′29″N–6°27′44″N, 5°36′10″E–5°36′37″E) using GPS mapping and WHO-recommended sampling procedures. Laboratory analyses covered pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, nitrate, sulphate, phosphate, and selected metals (Pb, Fe, Cr, Zn) determined by Atomic Absorption Spectrophotometry (AAS), alongside microbial tests for total coliforms and E. coli. The results (Tables 4.1–4.3, Figures 1–2) showed acidic groundwater (pH 5.19–6.14) below WHO limits (6.5–8.5), with low alkalinity (4–6 mg/L) and elevated metal concentrations: Pb (0.106–0.428 mg/L), Fe (2.98–7.51 mg/L), and Cr (0.37–3.87 mg/L), all exceeding the permissible limits of 0.01, 0.3, and 0.05 mg/L respectively. Potassium spiked at 55.8 mg/L in the borehole closest to the dumpsite (Sample 2), indicating direct leachate influence. Microbial tests showed absence of coliforms and E. coli, but minor heterotrophic bacteria (1 CFU/mL). Overall, the acidic and metal-enriched groundwater reveals significant leachate intrusion linked to dumpsite proximity, making the borehole water unsafe for domestic consumption without treatment. The findings highlight the need for controlled waste disposal, borehole siting regulation, and continuous groundwater monitoring in Iyowa.