While rain pelted most of KwaZulu-Natal last week, residents across the greater Durban North area experienced dry taps because surging algae levels are clogging dams and treatment systems.
uMngeni-uThukela Water, which supplies Durban with purified tap water, says filters are clogged due to a sudden increase in algae levels in the Albert Falls, Inanda and Nagle dams.
While some experts blame rising temperatures, environmental adviser Anthony Turton says the algae blooms stem from severe nutrient overload due to untreated sewage pouring into the water bodies.
“Those algae blooms are now blocking filters, but they are also potentially releasing their toxins into the water.”
He said most of South Africa's about 1,000 sewage treatment works have failed.
“This is almost always a municipal problem, but it affects all water boards like Umgeni. The water boards cannot control the municipalities so they can’t fix the broken sewage works. Then increased sewage flow — about 7-billion litres of water daily across the whole country — is nutrient rich so it flows into dams like Albert Falls, Inanda and Nagle.
“The increased nutrients drive biomass production — more nutrients means more living things that eat those nutrients. Two main types of biomass occur — floating biomass like water hyacinth and duckweed and suspended biomass like cyanobacteria. It’s the latter that cause algae blooms. Whenever a bit of warm weather happens those single-celled creatures multiply and bloom.
“The problem is that the cyanobacteria we have in South Africa are mostly of the genus Anabaena or Microcystis and each produce a series of potent toxins that become part of the water. Anabaena produce anatoxin and Microcystis produce microcystin toxin,” he said.
“I am predicting that 2025 will be the year that four major metros in South Africa fail. They are eThekweni, Ekhuruleni, Tshwane and Johannesburg. All four will fail because of water security problems. All four are major industrial areas, so their failure will trigger an economic crisis on a scale unprecedented in our history,” he said.
The director of the Institute for Water and Wastewater Technology at Durban University of Technology, Prof Faizal Bux, said the nutrient levels of dams should be regularly monitored, especially in summer, and the sources of pollution should be immediately addressed.
“Dealing with the problem downstream at the water treatment plant is costly for the water utility and immensely inconvenient to the end users. The department of water & sanitation’s recent Green Drop Report has highlighted the fragile state of our wastewater treatment plants. The water service authorities and service providers need to deal with this with the absolute urgency it deserves.”
Water Science CEO Stanton Govender called for a co-ordinated effort between local authorities, environmental experts and water management bodies.
“Municipal oversight often falls short in enforcing standards, allowing pollutants to enter water bodies unchecked. Addressing these issues requires more rigorous, proactive monitoring and strict policy enforcement.”
Residents and business owners in Durban’s northern areas, including Phoenix, have grappled with unpredictable water supply for nearly two years. Frustration is mounting over the perceived lack of transparency and urgency from uMngeni-uThukela Water, which operates the dams and water infrastructure for the region.
“We live in 2024, how is it that algae blooms are still crippling our water systems?” asked ward local councillor Heinz de Boer.
“People are rightfully asking why these blooms aren’t being pre-emptively monitored and treated.”
In a statement on Monday, uMngeni-uThukela Water spokesperson Siyabonga Maphumulo said the utility was continuing efforts to optimise its treatment processes.
“This includes using advanced chemical treatment methods to unclog its filters. Our water quality monitoring has also been increased to detect and act against the presence of algae in raw water from the Albert Falls-Nagle Dam system. uMngeni-uThukela Water continues to monitor the raw water quality and we anticipate that the problem will be resolved once the algal count from Albert Falls-Nagle Dam subsides,” he said.
Maphumulo said various factors contribute to increased algae, including higher temperatures.
However, the increased pollution of water sources, including through industrial and agricultural waste products, also has a direct effect on water pollution which increases algae at our dams.
“While uMngeni-uThukela Water, working with the DWS continues to monitor and treat water received from its dams, the increased pollution of water sources is the main contributing factor so there should be greater efforts to mitigate against polluted waste entering rivers.”
“We are continually treating our water at Durban Heights and we have already begun to see some improvements with an increased volume of water now being supplied to eThekwini from Durban Heights.”
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