Stones and Sand Clean Up Polluted South African River

Researchers at the University of Cape Town have developed a chemical-free system using stones, heat-treated wood, and sand to purify water from the polluted Stiebeuel River, making it safe for irrigation in the fast-growing informal settlement of Langrug. The Water Hub project treats roughly 36,000 liters daily, removing sewage, chemicals, and drug residues through a solar-powered filtration process. Researcher Kevin Winter says the system now eliminates about 99% of toxins, with most treated water returned to the river and a portion used to grow vegetables for local families. Since its 2018 launch, the project has only recently reached the bacteria-reduction threshold needed for safe irrigation, though the water still isn’t drinkable. Researchers believe the model could help other water-stressed communities cope with climate-driven droughts and support food security.