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 SO₄^2->Cl⁻>PO₄^3->NO₃⁻>Br⁻>NO₂⁻>F⁻. The concentrations of the water-soluble anions (except PO₄^3- and at some sites NO₃⁻) in samples were within their respective South African and/or WHO guidelines for irrigation water. However, the levels of PO₄^3- 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.

Keywords:

• Bon Accord Dam
• inductively coupled plasma-mass spectrometry
• ion chromatography
• sediment
• South Africa
• water

Public Interest Statement

Water resources are scarce in the world in general and in South Africa in particular. So the country is using man-made reservoirs (dams) for urban, industrial and irrigation purposes. Hence, the quality of the water in these dams is important. One of the dams is the Bon Accord Dam, the smallest impoundments in the Crocodile River catchment and found about 15 km north of central Pretoria, just north of the N4 highway. The Dam was completed in 1925 to supply irrigation water to areas for vegetable farming and hence its quality is of importance. Therefore, this study tries to assess the microbiological, physicochemical and elemental quality of the Dam.

Competing Interest

The authors declare no competing interests.

Acknowledgements

This work was funded by the National Research Foundation of South Africa and Tshwane University of Technology. Kebede Nigussie Mekonnen acknowledges Mekelle University, Ethiopia.

Additional information

Funding

The authors received no direct funding for this research.

Notes on contributors

Robert Ian McCrindle

The research group currently working to see the quality of the Dams found in South Africa focusing on Bon Accord Dam and Loskop Dams, South Africa. As a research group, we are working on the determination of microbiological and physicochemical properties of the water, sediment and biota. Besides we are working on the determination of the levels of inorganic and organic pollutants in the aforementioned samples in the aquatic environment. We are also working on the remediation mechanisms towards increasing the threats of the aquatic environment with respect to the inorganic and organic pollutants.