Assessment of heavy metals (Pb, Cu, Cr, Cd and Fe) in the groundwater wells in the vicinity of Nyanza Municipal Solid waste in Kigali City- Rwanda

Abstract

The purpose of this study was to assess the impacts of Nyanza Municipal Solid Waste (MSW) dumping site on groundwater. As many groundwater resources are contaminated by dumping sites that are poorly managed, the equally poorly managed Nyanza MSW dumping site in Kigali could have impact on people depending on groundwater for their daily activities. Leachate samples were taken at the edge of the waste bulk and groundwater samples were collected from the wells located in the vicinity of the dumping site. Sampling was done in dry and wet season using PE bottles. Heavy metals analysis was done using flame atomic absorption method. The analytical results of leachates samples (Pb: 4.5-8.5 mg/L, Cd: 0.20-0.75 mg/L, Cr: 16.8-5.7 mg/L, Cu: 0.8-2.8 mg/L, Fe: 39.2-130.2 mg/L) showed that heavy metals are leached out from the MSW. The analytical results of groundwater from the wells located in the vicinity of Nyanza MSW dumping site (Pb: 0.25-0.86 mg/L, Cd: 0-0.02 mg/L, Cr: 0-2.68 mg/L, Cu: 0.02-0.12 mg/L, Fe: 0.12-0.76 mg/L) compared to the groundwater from the Masaka well located far away from the site (Pb: 2.24 mg/L, Cd: 0.00 mg/L, Cr: 0.04 mg/L, Cu: 0.08 mg/L, Fe: 0.14 mg/L), revealed that groundwater from the wells located in the vicinity of Nyanza MSW dumping site requires further physical chemical treatment to ensure their suitability for human consumption as the levels of some water quality parameters exceeded the WHO guidelines for drinking water. Further analysis are needed with inclusion of hydrogeochemical of the area as very low concentration of heavy metals in interest were found in one of the well situated in the vicinity of Nyanza MSW dumping site. Therefore, Nyanza MSW dumping site might not be the only pollutant source for groundwater in this region.