CAPE TOWN: A nature-based filtration system developed by researchers at the University of Cape Town is treating around 36,000 litres of heavily polluted river water every day, making a portion of it suitable for irrigating vegetable gardens in a vulnerable community in South Africa’s Western Cape.
The Water Hub project uses a combination of stones, sand and heat-treated wood to clean water from the Stiebeuel River, which has been contaminated by sewage, chemicals and traces of drugs and pharmaceutical waste.
The treated water is not considered safe for drinking, but researchers say the system has reduced bacteria and pathogens to levels suitable for irrigation. Around 3,000 litres of treated water is retained for community vegetable gardens in Langrug, near Stellenbosch, while most of the remaining water is released back into the river.
According to Kevin Winter, one of the researchers behind the project, the system removes about 99% of toxins from the water.
“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,” Winter told The Guardian.
He said the treated water had improved significantly in quality, although it remains unsuitable for drinking.
How the Water Hub works
Established in 2018 at the site of an abandoned wastewater facility, the Water Hub repurposed old wastewater drying beds into a series of filtration cells.
The system operates off-grid using solar power. Polluted river water is pumped into the filtration cells, where it moves through several layers of natural materials over roughly five days.
The first stage uses large stones to capture particles and some chemicals. The water then passes through biochar, made by heating wood to around 800°C (1,470°F). The material helps remove contaminants including traces of pharmaceuticals, drugs and ammonia.
In the final stage, smaller stones and layers of sand filter out additional pollutants before the water is either returned to the river or diverted for irrigation.
Researchers say the relatively simple approach could be useful in communities where conventional water and wastewater infrastructure is difficult or expensive to establish.
Rapid population growth increases pressure
The project is particularly significant for Langrug, where the population has expanded sharply over the past two decades.
Winter, who has worked in the area since 2006, said the community has grown from around 3,000 people to more than 26,000. Much of the increase has been linked to seasonal employment on farms and in nearby Franschhoek.
The rapid and largely unplanned growth has placed pressure on existing water and sanitation infrastructure, leaving many residents without reliable access to clean water and adequate sewage facilities.
Instead of constructing an entirely new conventional treatment plant, researchers converted an abandoned wastewater facility into a nature-based treatment system tailored to the community’s needs.
Climate change adds to water insecurity
The Water Hub comes as the Western Cape faces increasing concerns over water scarcity and climate-related disruptions.
The region experienced a severe water crisis in 2018 after prolonged drought pushed reservoirs towards critically low levels. Households were forced to ration water, while around 31,000 farm workers lost their jobs.
Winter said such experiences highlight the need to develop alternative ways of securing water and food as climate conditions change.
“It’s absolutely crucial that we start looking at how we do this,” he said, warning that the region could face a combination of wildfires, flooding and prolonged droughts over the coming decades.
Designed for vulnerable communities
Winter stressed that the Water Hub is not intended to replace conventional wastewater treatment plants that serve large cities and handle industrial-scale volumes.
Instead, the project focuses on rural and vulnerable communities where large-scale infrastructure may be impractical or unaffordable.
Its use of solar energy and natural filtration allows the system to operate without chemical treatment while providing water that can support local food production.
For Langrug residents, researchers say the project demonstrates how polluted water can be transformed into a resource for growing food and improving community resilience.
“Making water available for food, and for food security, as a climate-change strategy is absolutely crucial worldwide and we’ve got to learn to be able to do that more and more,” Winter said.
