Evaluation of Surface Water Quality Using Various Indices for Heavy Metals in Sasolburg, South Africa

The purpose of the study was to determine the concentrations of heavy metals in surface waters used for domestic and farming activities. This study investigated various water quality parameters, including pH, electrical conductivity (EC), total dissolved solids (TDS), and major and trace elements such as Al, As, Cd, Co, Cr, Fe, Mn, Mo, Ni, Pb, Sb, Se, Sr, Tl, and V, which were investigated during the dry and wet seasons from samples collected at Meulsteenpan Lake, Coalplex Stream, and Natref Stream in Sasolburg, Free State, South Africa (2019–2020). The results revealed that the pH of water collected from Meulsteenpan Lake (7.86–7.89) and Coalplex stream (7.13–7.37) were within the Department of Water Affairs and Forestry (DWAF), World Health Organization (WHO), and Environmental Protection Agency (EPA) permissible guideline values for domestic and agricultural use. On the other hand, the pH from Natref stream (6.16–7.68) was within the permissible guideline values set by the DWAF for domestic use but below the permissible guideline values set by the WHO and EPA for domestic use, and the DWAF for agricultural use. The mean TDS and EC values in Meulsteenpan Lake (796–980 mg/L) and (1.20–2.00 mS/m) exceeded permissible guideline values set by the DWAF and WHO domestic use for TDS, Coalplex stream (309–326 mg/L) and (0.65 mS/m), and Natref Stream (269–413 mg/L) and (0.89–0.96 mS/m) were within the permissible guideline values for the DWAF and WHO domestic use for TDS. The results obtained for metal concentration revealed higher mean concentrations for Al, Fe, and Mo, Mn in the study area, which could pose adverse health risks to aquatic life and humans. Various pollution and health assessments (C<i>f</i>, m-C_d, m-HPI, HEI, NEI, and WQI) were used to evaluate the quality status of the surface water on all sampling sites. WQI revealed that in the wet and dry seasons, surface waters from Coalplex Stream and Natref Stream had “excellent” water quality, while Meulsteenpan Lake had “excellent” water quality in the dry season, but in the wet season, the water quality was “unsuitable for drinking”.