Assessment of microbiological, physicochemical, water-soluble anions and elemental contents of water and sediments of Bon Accord Dam, South Africa

Abstract Due to the scarcity of water resources, South Africa is mainly dependent on water stored in man-made reservoirs for urban, industrial and irrigation purposes. Hence, the quality of the water in these dams is important. The microbiological, physicochemical and elemental quality of water and sediment of Bon Accord Dam, South Africa were studied. The total coliform and Escherichia coli were measured, the physicochemical parameters were determined in situ and elemental analyses were carried out. The water from some sampling sites had pH>8.4, which could affect crop quality and yield. The electrical conductivity and total dissolved solid values implied that the water was of medium salinity where sensitive crops could be affected. The measured physicochemical parameters were within the national and/or international guidelines for irrigation water even if some of the parameters may have a negative impact on selected crops. The anion concentration in the water followed the order SO42->Cl−>PO43->NO3−>Br−>NO2−>F−. The concentrations of the water-soluble anions (except PO43- and at some sites NO3−) in samples were within their respective South African and/or WHO guidelines for irrigation water. However, the levels of PO43- in this study were ≥0.130 mg/L makes the dam hypertrophic. The average concentration of potentially toxic elements in the sediments of the dam was found to be moderately to heavily polluted by Cr and Ni, non-polluted to moderately polluted by Cu and non-polluted by Pb and Zn. The bacterial levels in the dam were low and can hence not be considered a problem.