Hope for Hartbeespoort Dam water quality as new ‘nanobubble’ technology starts to bite

Notorious for its hypertrophic waters, Hartbeespoort Dam is benefitting from an experimental project to clean it up.

The project, spearheaded by BluePlanet South Africa, is an effort to harvest and biocontrol invasive hyacinth through oxygen transfer technology.

Marcel Esterhuysen, operations director for BluePlanet SA told Daily Maverick that the company was selected after a request-for-information process by the Department of Water and Sanitation (DWS) and Magalies Water in 2023.

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David Magae, spokesperson for Magalies Water, told Daily Maverick that BluePlanet SA’s involvement at the dam was a research project and trial, not necessarily a fully implemented project.

“BluePlanet SA is expected to install and operate a nanobubble generator. They are also expected to train employees from Magalies Water and DWS on the operation of nanobubble technology,” said Magae.

The company’s website says that nanobubble technology collects water in the air, and, through a generator which requires 300 watts to power, converts the oxygen into ozone which decomposes organic matter and odours, killing pathogenic bacteria.

More than half of Hartbeespoort Dam has been covered with hyacinth since the beginning of 2023. (Photo: Ethan van Diemen)

The method also increases dissolved oxygen in the water, activating the decomposition of microorganisms in water or river sediment.

Over a month, the combination of the nanobubbles and water flow react to break down pollutants such as E.coli bacteria and total coliforms, increasing water transparency.

Mogae said that “the water quality in the pilot site has improved drastically and the impact is extending to the entire dam. There is a notable increase in oxidation-reduction potential (the measure of a water body’s ability to cleanse itself) and dissolved oxygen, accompanied by a drastic reduction in nutrients and an improvement in water quality.”

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But John Wesson, regional chair of the Wildlife and Environment Society of SA, told Daily Maverick that a part of the community had concerns about the use of the technology without it having proof-of-concept on a large body of water like Hartbeespoort, which covers over 2,000 hectares. The method is usually deployed on smaller bodies of water.

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“Hartbeespoort can’t afford to experiment. When we look at the livelihood of the people at the dam, such as tourism, relying on an experiment will take about three years to show results and that won’t work.

“That means the community is going to invest in potential results and if it doesn’t work, the dam will still be in a bad state,” said Wesson.

He also raised questions about the amount of electricity the generator would require and the cost of that to the community. He said there were concerns about the technology increasing oxygen levels that act as a flocculant, causing sediment to settle at the bottom of the dam, thus adding to nutrient density.

Currently, 8% of the dam is covered in hyacinth.

The Hartbeespoort Dam was more than 60% covered in hyacinth from the beginning of 2023. (Photo: Julia Evans)

Wesson suspects that, given the manner in which the plants are dying, the decrease is a result of chemical spraying.

Esterhuysen maintained that in the short period of time the trial had been underway — it began at the end of January 2024 — there had been encouraging signs in the area where the generator had been placed.

The project is expected to run for a year.

Esterhuysen said he was unable to share specifics of the data due to a non-disclosure agreement between the company and Magalies Water. The entity would also not divulge how much money was being spent on the trial.

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Magae said: “The plan is mature and fully crystalised, and it is yielding the desired outcome. The intervention enacted by Magalies Water is unique, novel and one of a kind.

“This turnaround strategy has improved the water quality of the Hartbeespoort Dam and reduced the dam coverage by floating plants. This is an impressive milestone.

“However, the premier quest is to curb nutrients loading at source using a myriad of proven and tested technologies for nutrients attenuation and water amelioration.” DM

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