South Africa's AMD/wastewater is 'mineable'- Turton
Volume: Volume 2, issue 1 |  Friday, 28 January 2011 |  Martin Creamer  |  0 comment

Joe Zambelli

JOHANNESBURG (miningweekly.com) – Consideration should be given to studying the economic feasibility of “mining” South Africa’s problematic acid mine drainage (AMD) and wastewater for metals, minerals, salt and even hydrogen, says Touchstone Resources director Dr Anthony Turton.

Turton is a protagonist not only of “mining” AMD, but also the water in sewage works and obtaining phosphate, which is crucial for food security, as a byproduct.

“Sewage works can start becoming phosphate mines,” he says.

Last year, environmental solutions developer Earth Metallurgical Solutions (EMS) reported that it had successfully recovered metal nitrates from AMD.

Turton tells Mining Weekly Online in a video interview that one of the key problems in the current AMD thinking is that the acidic water volumes are too small to be economic.

But by combining the AMD and sewage water streams, volumes may be increased to a point of providing economic viability.

Turton favours consideration being given to the use of ion-exchange technology to remove the metals and minerals.

“Ion exchange actually ‘mines’ the water,” he says, adding that innovative new water-treatment technologies are also likely to emerge in the near future.

He advocates that the large volume of salt that becomes available in processing AMD should be considered for use in concentrated solar power plants.

He estimates that for every litre of AMD, up to 4g of sulphate salt are produced, plus a range of acid-leached metals and minerals. Much of the phosphate in wastewater treatment works comes from personal care products like shampoos and soaps.

Simultaneously, the water will be sufficiently cleaned for safe discharge back into natural streams, or be cleaned to potable standard, and then injected into an aquifer to overcome psychological barriers.

There is also the prospect of AMD being considered as a feedstock for a hydrogen economy, with the possibility of using renewable energy to provide the electricity to crack water into its hydrogen and oxygen parts

In correcting the mispricing of water, a cue can be taken from the successful water project in eMalahleni, where an Anglo American-BHP Billiton joint venture is turning AMD into drinking water at R10 to R12/m³.

“If we look at a realistic price of water, suddenly the AMD problem goes from being a problem into becoming a major asset,” Turton comments to Mining Weekly Online.

He believes that a well-considered government policy pronouncement can create the enabling environment for venture capital to be attracted into experimental AMD/wastewater ventures.

AS EMS CEO Richard Doyle reported earlier, field trials have been carried out with mining explosive company AEL, to show that “the AMD problem can be blown out of the water”.

AEL intends incorporating EMS’s recovered nitrate into its bulk surface formulation.

EMS notes that what sets its technology solution apart is that it does not produce any byproducts in its AMD treatment process, with most other solutions often generating brine.

The EMS process produces potable water, fertilisers and explosives, with the company also able to convert the metal nitrates into thermal salts, which can be used for thermal storage in concentrated solar power plants.

A team of experts appointed to advise the South African government on AMD has recommended a number of short-term measures benchmarked on the experience of some countries that have encountered AMD challenges, such as Canada and the US.

The team held a follow-up meeting with the Inter-Ministerial Committee in December, to discuss its revised report and recommendations. An initial report, tabled in October 2010 but not made public, was referred back to the team of experts for further work.