Scientists in Scotland and South Africa have developed a method to convert hazardous acid mine drainage (AMD) into a valuable resource which can be used to treat water for potable purposes, thereby offering hope for communities living near polluted mining areas.

The research was presented at the International Mine Water Association (IMWA) 2025 conference, which was held in July, in Portugal and Spain.

The project could help transform a major environmental hazard into an economic opportunity, states University of South Africa’s (Unisa’s) Professor Vhahangwele Masindi.

The study involved collecting mine water from an active coal mine in Mpumalanga, South Africa. 

The researchers in the Johannesburg and Edinburgh team used magnesium oxide nanoparticles, produced from the calcination of locally available cryptocrystalline magnesite, to precipitate iron from the AMD before reacting it with hydrochloric acid to produce ferric chloride – a widely used water treatment chemical.

“Active and derelict coal and gold mines in South Africa discharge close to 400-million litres of AMD per day, and this demonstrates the viability of using this wastewater stream as a secondary mine for valuable minerals,” he says.

This approach supports the circular economy by turning waste into a product with real value and also helps reduce the environmental footprint of mining operations, adds Masindi.

AMD is a toxic byproduct of mining that is notorious for contaminating rivers and groundwater with high concentrations of metals such as iron, aluminium and manganese.

AMD can also make water undrinkable and destroy entire ecosystems, as well as destroy infrastructure like bridges and pipelines.

In laboratory tests, the AMD-derived ferric chloride achieved removal rates of over 99% for pollutants such as aluminium, iron and chromium from river water. 

The treated water met South Africa’s drinking water standards, which include South African National Accreditation System, International Organisation for Standardisation and International Electrotechnical Commission 17025 accreditation.

Broad Scale Integration

The research findings show how global mining regions could benefit from processing AMD and recovering valuable products, says Heriot-Watt University Research Centre for Carbon Solutions associate Professor Dr Spyros Foteinis, who collaborated on the research.

“We’re demonstrating that even highly contaminated mine water can be cleaned up. This could be a low-energy and low-carbon practical solution to a problem that blights communities around the world and has lasting health, ecological and economic impact,” he says. 

The scaling up of this sustainable technology can underpin global efforts to manage industrial waste more sustainably and advance the global effort for clean water and sanitation for all, adds Foteinis.

Going forward, the research team’s next steps are to pilot the technology and its use in rural and peri-urban communities in South Africa which struggle with water scarcity pressures, and further afield.

The scientists say their method could be applied at an industrial scale, particularly in countries grappling with legacy mining pollution.

Climate change is exacerbating water scarcity pressures and creates new challenges that the water sector needs to address sustainably, adds North West province potable bulk water supplier Magalies Water water quality and process specialist assistant, and Unisa PhD student Mamile Mahlohla.

“This technology can be part of a portfolio approach. We’re also working on different methods of recovering nutrients and clean water from municipal wastewater,” she says.