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

Scientists say system to treat contaminated wastewater offers a model for ensuring food security in a fast-warming climateAll it took to turn the murky, heavily polluted waters of South Africa’s Stiebeuel River into a resource clean enough for irrigating a community’s vegetable plots was a collection of stones, heat-treated wood and sand.Without chemicals and using renewable energy, researchers from the University of Cape Town are cleaning 36,000 litres of water, polluted by sewage,