Researchers from the University of Cape Town are using a natural filtration system to clean 36,000 litres of water daily from South Africa's Stiebeuel River. The system, which uses stones, heat-treated wood, and sand, makes the heavily polluted water suitable for irrigating community vegetable plots.
The Water Hub project, located in Langrug near Stellenbosch, operates without chemicals and uses renewable energy. It treats water contaminated by sewage, chemicals, and traces of drugs, making it usable for growing food in an informal settlement.
Kevin Winter, one of the researchers, stated that the system removes approximately 99% of toxins before most of the water is returned to the river. About 3,000 litres are retained daily to irrigate food-producing gardens at the Water Hub. The project, established in 2018, has this year successfully reduced bacteria and pathogens to levels safe for irrigation, though not for drinking.
The off-grid system, built in an abandoned wastewater site, pumps river water into filtration cells using solar power. Over five days, the water filters through large stones, a layer of biochar (wood burned at 800C), and final layers of smaller stones and sand to remove particles, chemicals, drug traces, and other pollutants.