Characterization and risk evaluation of water samples collected from boreholes situated around a dumpsite in Obalende, Lagos, Nigeria

Abstract

Dumpsites are used worldwide for waste disposal because they are cost-effective and have the capacity to contain enormous amounts of waste. However, concerns are rife about the impact of dumpsites on the quality of nearby groundwater. The present study assessed the quality of borehole water near a dumpsite in Obalende, Lagos, Nigeria. Heavy metal, physico-chemical, and microbiological tests were performed on the samples of the water using standard techniques, and the results were compared to the WHO permissible limits. The average daily oral ingestion (ADOI), average daily dermal ingestion (ADDI), and hazard quotient (HQ) of the heavy metals were also estimated. The heavy metal analysis revealed non-permissible levels of zinc, iron, lead, and manganese, while nickel, cadmium, and silicon were within the permissible limits. Physico-chemical analysis showed that turbidity, total suspended solids, total dissolved solids, nitrate, and phosphate were within the permissible limits, but not the pH, electrical conductivity, chloride ion, sulphate and dissolved oxygen. The microbiological examination indicated that the water had high levels of bacteria and coliform counts. The HQ of Zn, Fe, and Pb, mainly through dermal exposure was above the recommended limits (>1). Overall, the results suggest that the water may predispose consumers in the area to Zn, Fe, Pb, and Mn toxicities as well as microbial infections. Consequently, consumers are advised to treat the water before consuming it.

Keywords

• average daily ingestion
• bacteria
• dumpsite
• lead
• nitrate