1. School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment; University of the Witwatersrand; Wits 2050 Johannesburg South Africa
2. Department of Chemical Engineering, College of Engineering; Covenant University; Ota Nigeria
3. Microbiology and Environmental Biotechnology Research Group; Agricultural Research Council - Institute for Soil, Climate & Water 600; Belvedere Street, Arcadia 0001 Pretoria South Africa
4. Unit for Environmental Science and Management; North-West University (Potchefstroom Campus); Potchefstroom 2520 South Africa