The City of Cape Town is testing two water remediation technologies along the Big Lotus River as part of a pilot project aimed at improving water quality before polluted flows reach Zeekoevlei.
The pilot, which was introduced in May, is being carried out at several points along the river, where pollution from different sources has contributed to deteriorating water quality.
The City’s Water and Sanitation Department is using its Scientific Services Branch to assess whether biobags and nanobubbles can reduce some of the pollutants affecting the river, as noted by the City.
The biobags contain biochar made from pine wood and inoculated with naturally occurring microbes. The City is testing whether they can help lower levels of nutrients and organic matter in the water.
The second intervention uses a nanobubble unit that produces extremely small bubbles in the water. Preliminary studies by the City indicate that the technology could assist in reducing odour, solids and organic loads.
The pilot forms part of efforts to better understand the pollution entering the Big Lotus River before it eventually reaches Zeekoevlei, where high nutrient levels can contribute to algal blooms.
The condition of the Big Lotus River matters beyond the river itself, as its flows ultimately enter Zeekoevlei.
Elevated nutrient levels in a water body can encourage excessive algal growth. Some algal blooms can produce toxins, potentially affecting the health and recreational use of the water.
The City has stressed that the project is intended to establish whether the technologies produce measurable results rather than provide an immediate solution to the river’s pollution problems.
‘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,’ said the City’s Mayoral Committee Member for Water and Sanitation, Councillor Zahid Badroodien.
He said the findings could potentially help guide future interventions in Zeekoevlei and other waterways if the pilot proves successful.
Scientific Services is collecting water samples at the pilot sites, with the results being assessed over time to determine how effective the two interventions are.
The monitoring will look at changes in water quality and help establish whether either technology could eventually be considered for use at other locations.
Badroodien also noted that different waterways face different pollution pressures.
‘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,’ he said.
The pilot gives the City an opportunity to test both technologies under local conditions rather than relying solely on results from elsewhere.
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