The City of Cape Town is testing two water-remediation technologies along the Big Lotus River to reduce pollution and improve water quality flowing into Zeekoevlei.
The pilot project, introduced in May 2026, is being conducted at multiple sites along the river, where polluted inflows from several sources have contributed to declining water quality.
The Big Lotus River ultimately flows into Zeekoevlei, making interventions upstream important to the health of the wider water system. High nutrient levels in the vlei can contribute to algal blooms, some of which may produce toxins and affect the health and recreational use of the water body.
The City’s Water and Sanitation Scientific Services Branch is testing two different technologies to determine whether they can provide measurable improvements.
The first involves biobags containing biochar made from pine wood and inoculated with naturally occurring microbes. Researchers are assessing whether the intervention can reduce nutrients and organic matter in the water.
The second technology uses nanobubbles, extremely small bubbles introduced into the water through a specialised unit. The technology has been used internationally in attempts to remediate polluted water bodies, while the City’s preliminary studies indicate it may help reduce odour, solids and organic loads.
“We are testing whether these technologies can make a measurable difference in one of the city’s important inland water systems,” said the City’s Mayoral Committee Member for Water and Sanitation, Councillor Zahid Badroodien.
Badroodien stressed that the project is not intended as an immediate solution to the broader pollution challenges affecting Cape Town’s waterways.
“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,” he said.
The pilot reflects an evidence-based approach in which potential environmental technologies are tested and monitored before decisions are made about wider implementation.
“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,” Badroodien added.
The City’s Scientific Services Branch will collect and analyse water-quality data throughout the pilot to measure the effectiveness of both technologies over time.
The results will determine whether either intervention could be considered for wider use in Zeekoevlei or other waterways facing similar pollution pressures.
If successful, the pilot could provide Cape Town with additional tools for improving inland water quality while helping authorities identify which remediation approaches are most effective under different environmental conditions.
