How a South African town cleaned up its polluted river using stones, wood and sand

Researchers at the University of Cape Town are treating 36,000 litres of sewage-polluted water daily using a chemical-free filtration system of stones, heat-treated wood and sand, removing nearly 99% of toxins before returning it to the river and using 3,000 litres daily to irrigate vegetables for an informal settlement near Stellenbosch.

The system treats water for irrigation; it is not yet approved for drinking water. The project began in 2018 and only this year achieved pathogen levels suitable for irrigation use.