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Fears of long term damage to SA's water supply as eutrophication strangles rivers and dams | IOL

Written by  Tuesday, 07 July 2020 19:13
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Toxic green algae in the Vaal River is caused by eutrophication, which harms water quality and impacts river life.     Supplied
Toxic green algae in the Vaal River is caused by eutrophication, which harms water quality and impacts river life. Supplied

Article by Sheree Bega

The black, sewage-contaminated water that flows from the Rietspruit into the Loch Vaal is so polluted that even algae struggles to grow in its polluted depths.

“All we get is black sewage sludge in areas where there’s less current,” explains Mike Gaade, who lives on the banks of the Rietspruit in Vanderbijlpark.

But sightings of cyanobacteria blooms of toxic blue-green algae in the main Vaal River, caused by sewage, are becoming more frequent, particularly in summer, he says.

That the Vaal is becoming eutrophic is a real concern, says water scientist Professor Anthony Turton.

Eutrophication causes an overgrowth of algae that harms water quality, reduces oxygen, produces toxins, impacts river and marine life and affects food and human health.

“Once a water body becomes eutrophic and cyanobacteria becomes established, no known method in SA has ever been able to reverse that process,” Turton explains.

SA’s most eutrophic water is in Hartbeespoort Dam - the most studied of all systems. “Despite the very best scientists being unleashed on the problem, we have been unable to restore the system to its previous trophic status. With our current available knowledge, it’s safe to believe the Vaal is now becoming eutrophic and this is going to persist as the the new normal.”

Eutrophication is the “logical outcome” of discharging high levels of phosphates and nitrates into river systems - natural nutrients that drive the production of plant biomass. “Biomass typically takes two forms in SA - the familiar problem of water hyacinth at Hartbeestpoort Dam and the cyanobacteria blooms of blue-green algae that the Vaal is now succumbing to.”

The Department of Water and Sanitation (DWS) has now released its draft inception report for its National Eutrophication Strategy. The strategy, with its 10-year horizon, seeks to provide guidance to the DWS and water sector at large “on strategies to avoid, reduce, mitigate and manage the effects of eutrophication on SA’s water resources”.

It notes that the project was initially started in 2002 and “never completed” but was reinstated last year.

“The issue of eutrophication had not received adequate attention, previously, which could have been one of the reasons the situation exacerbated even more,” reads the report.

The Integrated Water Quality Management (IWQM) Policies and Strategies for SA in 2016 and 2017 "emphasised eutrophication as one of the country’s pressing water-quality challenges, along with salinisation, acid mine drainage, urban pollution and sedimentation”, it states.

Eutrophication, says Turton, is an old problem that has now reached “catastrophic proportions” due mostly to the failure of the DWS in its role as national regulator. “DWS has allowed the Blue and Green Drop Reporting Standard to fall into dysfunction. This has allowed municipalities to act with impunity knowing they will never be sanctioned for non-compliance. The biggest culprit is the 824 wastewater treatment works (sewage plants) we have in every municipality. About 60% of them are now dysfunctional, so they collectively discharge over 5billion litres of sewage into our rivers daily. We draw our drinking water from those same rivers.”

No bulk water provider in the country that takes water from a river and produces potable water uses technology capable of removing the toxic by-product of eutrophic water: microcystin. “This is a potent molecule that is released when the cyanobacteria is distressed. The molecule becomes parts of the water and cannot be filtered out from the water.

“This means that South African citizens will increasingly be exposed to microcystin as long as our wastewater plants continue to fail.

“Eutrophication is a slow onset disaster that will plague SA for the next generation. The manifestation will increasingly be in the form of low dose but long-term exposure to microcystin. The coronavirus has merely added a new complication, because of the potential for faecal-oral transmission through contaminated rivers.”

Satellite work by the CSIR has already revealed that 60% of the country’s dams are eutrophic.


Sightings of blue-green algae, caused by sewage, is becoming more frequent, especially in summer. Supplied

In his 2015 paper, “Living with Eutrophication in SA: A review of realities and challenges”, scientist William Harding noted how the socio-economic well-being of SA is largely dependent on reservoir lakes, with between 41% and 76% of total storage eutrophic or hypertrophic.

“This is in stark contrast to a claimed 5% made by the DWS. Data and information on the incidence and toxicity of cyanobacterial blooms are sparse, yet severe problems exist The most seriously impacted reservoirs are located in the economic heartland of SA, which has an extant regional water-quality crisis.”

Many of SA’s rivers, reservoirs, and coastal lakes “no longer have the resilience to assimilate nutrients or sequestrate toxicants”, the paper found.

“The responsible agency (DWS) urgently needs to establish a reservoir management programme that embraces remaining individual and institutional memory, integrates all available knowledge and scientific findings, prioritises needs and acquires those skills and resources necessary to meet what is likely to become a crippling legacy of inaction.”

Eutrophication is a “big challenge and the situation is worsening”, says CSIR senior researcher Dr Melusi Thwala, who studies emerging environmental pollutants and water quality. “However, it is mostly dams/large impoundments that have historically faced such a challenge because they act as reservoirs in which pollutants such as nutrients can accumulate over time.

“For instance, in excess of 40% of approximately 500 large impoundments are eutrophic and others exhibit a character of non-natural nutrient enrichment.

“For river systems more and more cases are being observed but in smaller systems the rainy season can provide a dilution relief effect, but not so much in large systems such as the Vaal and Olifants rivers.”

Their hard-working nature means that large river systems receive continuous and large nutrient inputs from various anthropogenic (human-caused) activities, with “municipal wastewater treatment works being a priority input source due to their declining capacity to treat wastewater”.

“Simply put, the more human settlements, the more sewage waste is produced, sometimes exceeding the volumes that wastewater treatment works can handle. Agricultural and industrial activities also contribute nutrients into rivers,” Thwala says.

Mariette Liefferink, the chief executive of the Federation for a Sustainable Environment, says the most important drivers of eutrophication are dysfunctional waste water treatment works, dense informal settlements without proper sanitation, vandalism of sewage reticulation systems and sewage spills over many years into receiving streams.

“The tipping point has already been reached, beyond which, our ecosystems can no longer absorb and process the nutrients and other pollutants being passed on to it.”

The actions proposed by the National Water and Sanitation Master Plan is to by 2020, “identify and prosecute big polluters across the country (including municipalities), with a national communication campaign to accompany the action inclusive of reviving the Blue Scorpions”.

“The above-mentioned actions must be implemented concurrently with the development of the National Eutrophication Strategy," she says. "Failure to prosecute municipalities and other polluters will render the objectives of the strategy impotent.”

Eutrophication is a core priority of the Integrated National Water Resource Strategy and was identified as an issue of concern by the DWS in 2009.

It was highlighted in the Continuation of the Integrated Vaal River System Reconciliation Strategy Study (Phase 2) in March last year as an "unaddressed issue of concern".

Tackling it is entirely reliant on activities performed within the DWS, catchment management agencies (CMAs), together with other institutions within the water sector, Liefferink says. “However, the lethargy in completing the roll-out and delegations to CMAs is a major issue of concern. The development of the strategy is at risk to be aborted unless CMAs become functional.”

Eutrophication is a "crisis of unprecedented proportions", says Turton made all the more problematic because few people outside of the aquatic sciences and environmental health community "are aware that such a problem even exists”.

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