1. Water Research Group, Unit for Environmental Sciences and Management, Potchefstroom Campus, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
2. Laboratory for Electron Microscopy, Potchefstroom Campus, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa
3. Unit for Environmental Sciences and Management, Potchefstroom Campus, North-West University, Private Bag X6001, Potchefstroom, 2520, South Africa