Innovative River Filtration Boosts Food Security in South Africa’s Western Cape

Researchers at the University of Cape Town have built an off-grid filtration system on the Stiebeuel River near Langrug. Large stones trap particles, a biochar layer (wood heated to 800 °C) removes pharmaceutical residues and ammonia, and finer stones and sand absorb remaining toxins. Solar-powered pumps move river water through the cells, where it filters slowly over five days before being released back to the river. The design is intended for rural and informal-settlement use rather than for municipal-scale industrial treatment.

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Langrug’s population has risen from roughly 3,000 residents in 2006 to more than 26,000, driven by seasonal farm work and proximity to the affluent town of Franschhoek. The settlement’s expansion left many without reliable water or sewage services, stretching municipal plants beyond capacity. The Western Cape experienced an almost catastrophic water shortage in 2018, when reservoirs neared depletion and thousands of farm workers lost jobs. Researchers view the filtration system as a climate-adaptation measure to secure water for food production as droughts become more frequent.

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• The system treats about 36,000 litres of river water each day.

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• 99 % of toxins are removed before the water re-enters the river.

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• Approximately 3,000 litres per day are retained for irrigation of community vegetable plots.

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• The project, established in 2018, achieved bacterial and pathogen reductions sufficient for irrigation only this year.

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Project lead Kevin Winter notes that the treated water is indistinguishable in taste and clarity from municipal supply, though it is not intended for drinking. He emphasizes that the technology complements, rather than replaces, conventional treatment plants. Winter also stresses the urgency of developing such solutions, citing projected climate shifts that will bring more frequent droughts, wildfires, and flooding, all of which threaten water availability and food security.

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• “What we’re doing is taking that water, treating it every day, and some of that water is now being used for growing vegetables, for feeding hungry children and people living in the informal settlement,” — Kevin Winter

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• “It’s absolutely crucial that we start looking at how we do this. Climate in the next 30 years, particularly in our region here, is going to look very, very different,” — Kevin Winter

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