1. Research and Development Department, Namibia Water Corporation, Windhoek, Namibia
2. Department of Microbiology, Stellenbosch University, Matieland, South Africa
3. Centre for Environmental Management, University of the Free State, Bloemfontein, South Africa
4. Department of Chemistry and Biology, Toronto Metropolitan University, Toronto, Canada
5. Mathematical Statistics and Actuarial Science, University of the Free State, Bloemfontein, South Africa