City pilots innovative technologies to tackle pollution in Big Lotus River and Zeekoevlei

20 August 2026

The City of Cape Town is testing two innovative water remediation technologies along the Big Lotus River, in a pilot project aimed at reducing pollution and improving water quality before it reaches Zeekoevlei.

The pilot was implemented in May 2026 at multiple sites along the Big Lotus River, which has been affected by inflows of polluted water from several sources. These pollution occurrences have caused declining water quality in the river, which ultimately flows into the Zeekoevlei.

Caption 1: Alunge Sobekwa from Water and Sanitation's Scientific Services, using titration to analyse a water sample from the Big Lotus River inside a mobile testing laboratory.

High levels of nutrients in the vlei can fuel algal blooms, some of which can produce toxins and affect the health and usability of the recreational water body.
 
Water and Sanitation’s Scientific Services Branch is testing two remediation technologies at these sites.

• Biobags: These bags contain biochar made from pine wood and have been inoculated with naturally occurring microbes. The intervention is being tested to determine whether it can help reduce nutrients and organic matter in the water.
• Nanobubbles: A nanobubble unit has been installed to produce extremely small bubbles in the water. The technology has been used internationally in efforts to remediate polluted water bodies. The City’s preliminary studies suggest that it may help reduce odour, solids and organic loads.

Caption 2: Celine Meyer from Water and Sanitation’s Scientific Services, collecting a water sample from the Big Lotus River for analysis.

‘We are testing whether these technologies can make a measurable difference in one of the city’s important inland water systems. This is not a quick fix. It is a scientifically monitored pilot designed to establish what works, under which conditions and at what scale. If successful, the lessons could help inform future interventions in Zeekoevlei and other waterways.
 
‘There is no one-size-fits-all solution to polluted waterways. Each river, wetland and vlei has different characteristics and pollution pressures. Scientific monitoring and evidence-based decision-making are therefore essential,’ said the City’s Mayoral Committee Member for Water and Sanitation, Councillor Zahid Badroodien.

 
The pilot will be closely monitored by the City’s Scientific Services Branch, with water quality data collected, assessed and analysed for effectiveness over time. This will determine whether either technology could be considered for use elsewhere.