How Reverse Osmosis Plants Will Combat Acid Mine Drainage and Minimise Water Stress in Gauteng

A bold new chapter in water reclamation: Government turns to high-tech reverse osmosis to treat toxic mine waste and safeguard Gauteng’s water future.

Engineering a Cleaner Future for Gauteng’s Water

As climate change, urban sprawl, and industrial pollution intensify pressure on Gauteng’s fragile water systems, the South African government is taking a bold step. They aim to address a legacy issue rooted in the province’s gold-mining past: acid mine drainage (AMD).

Through the installation of reverse osmosis packaged plants — each capable of treating one million litres per day — officials hope to mitigate the spread of toxic, highly acidic mine water. They plan to optimise water reuse, especially in the water-scarce basins of the Witwatersrand.

The AMD Problem: A Century in the Making

The genesis of AMD lies in Gauteng’s mining history. For over 100 years, gold mines thrived across the Witwatersrand. To reach the ore, massive volumes of groundwater had to be pumped out. When mining ceased, so did the pumping — and mine voids began filling with water.

The exposure of sulphide-bearing rock to oxygen and water initiated chemical reactions that generated acid mine drainage. This water is laced with heavy metals, radioactive atoms, and high salt concentrations.

This environmental hazard now seeps into rivers and underground systems, threatening ecosystems, livestock, agriculture, and public health — particularly in the Eastern, Central, and Western Basins of the Witwatersrand goldfields.

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The Proposed Solution: Reverse Osmosis Packaged Plants

In response, the Department of Water and Sanitation (DWS), in partnership with the Trans Caledon Tunnel Authority (TCTA), has submitted a proposal to the Department of Forestry, Fisheries and the Environment. They aim to amend the existing environmental management programme.

The amendment includes installing reverse osmosis packaged units at the Central and Eastern Basins. These systems aim to:

• Extract harmful salts and metals from AMD water
• Reduce sulphate and manganese levels in discharged water
• Recycle and reuse water within treatment plants (especially in the lime mixing process)
• Reduce reliance on potable water for industrial purposes

Reverse osmosis is widely regarded as a best-practice method for treating saline or toxic water. It uses pressure to force water through membranes that remove contaminants.

“This intervention is expected to have a neutral or positive environmental impact,” the department noted. “No additional solid or liquid waste will be produced apart from the brine sludge.”

Environmental Benefits and Sustainability

According to the department’s application, the plants will significantly improve resource efficiency, particularly in water recycling efforts. Rather than discharging untreated AMD or relying on precious potable water for processing, the proposed system will:

• Promote circular water use
• Alleviate pressure on municipal water supplies
• Contribute to cleaner discharges into the Vaal River system

This approach aligns with South Africa’s growing need for resilient infrastructure that addresses both legacy pollution and current-day resource scarcity.

Support and Concerns from Environmentalists

The project has received cautious support from watchdog groups like the Federation for a Sustainable Environment (FSE). CEO Mariette Liefferink applauded the initiative’s alignment with water reuse best practices, especially in scenarios where pollution elimination isn’t immediately possible.

However, the FSE warns that the treatment plants still pose environmental concerns due to the concentration of salts and metals in the discharged water. Data provided by TCTA and the DWS reveals:

• Central Basin AMD plant: Treats 69 million litres daily, with sulphate levels around 2 728 mg/l (versus the acceptable 200 mg/l)
• Eastern Basin AMD plant: Pumps 101 million litres daily, discharging water with 1 122 mg/l of sulphates

Furthermore, manganese levels from both plants also exceed resource quality objectives, adding to the burden on the Vaal Barrage system.

“While the short-term solution has prevented releases from the Vaal Dam for dilution, salt concentrations downstream remain a major concern,” Liefferink said.

Addressing Gauteng’s Water Stress

One of the most pressing reasons behind this intervention is the ongoing water crisis in Gauteng. The DWS has warned that the continued use of potable water for industrial processes like AMD treatment is unsustainable.

“Potable water must be preserved for essential domestic purposes,” the department emphasized.
“If the amendment is not granted, this could negatively impact water conservation and resource management in the province.”

What Happens Next?

While the exact cost of the reverse osmosis intervention remains undisclosed, the environmental and human benefits are expected to far outweigh the financial investment.

The success of this model could open the door to additional reverse osmosis rollouts across the country. This is especially important in post-mining landscapes where toxic wastewater continues to accumulate.

A Step Toward a Cleaner, Safer Water Future

The government’s planned installation of reverse osmosis plants in the Eastern and Central Basins of the Witwatersrand is more than a technical upgrade. It’s a critical environmental and social intervention.

By neutralising acid mine drainage and recycling water in one of the country’s most densely populated regions, South Africa is moving toward a future where water sustainability and pollution control are not mutually exclusive.

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