Disputes between government and mining companies over the cost of cleaning up the toxic water caused by mining have led to the rapid rise in the water level following the partial closure of a water treatment plant outside Randfontein.

The toxic tide, called acid mine drainage (AMD), has filled an underground void called the Western Basin, which covers hundreds of square kilometres between Krugersdorp and Randfontein.

Department of Water and Environmental Affairs regional director for Gauteng Marius Keet tells Mining Weekly that the water level in the basin has reached a very critical level at 0,6 m below the surface. 
“It has the potential to start decanting at any moment. The decant of AMD into the Tweelopies Spruit would sterilise the total system downstream.”

He says that the Rand Uranium mine has never stopped pumping and partially treating the AMD, and that Mintails and DRDGold were instructed by the department to start the pumping and treatment of the water in the basin from July 1, 2009, although this will only be partial treatment.

Keet says that only high-sulphate levels and, to a lesser extent, manganese levels could have negative effects downstream of the discharge point. 
“However, this should always be seen as an interim solution addressing the immediate 
potential crisis that AMD could have.”

Acid water is also fast filling up two other underground caverns, a central basin beneath Johannesburg and Soweto stretching as far as Alberton, and an eastern basin beneath the East Rand as far as Nigel and Springs.

If left unchecked, this water could also 
decant and contaminate water that ultimately 
flows into the Orange river.

In the past, pumps kept gold mines outside Johannesburg largely free of water because most water was pumped to the surface, partially treated and released into rivers. 
Now many of the gold mines have closed or can no longer afford to keep pumping, and vast 
underground areas are filling up.

DRDGold’s spokesperson says that its subsidiary, West Wits Mining, is assisting with the funding of water treatment through Mintails’ Mogale water treatment plant with revenue from the sale of rock.

“However, the National Nuclear Regulator (NNR) stopped the selling of this rock, even though it had been tested and found to be clear for public release.

“Unless the NNR allows the sale of rock 
to continue, West Wits cannot assist further 
øwith the financing of water treatment,” he states.

NNR spokesperson Gino Moonsamy responds that during a recent ad hoc inspection, the NNR established that West Wits was releasing waste rock without having 
obtained authorisation for this activity from the NNR.

“The NNR views this as an act of noncompliance with the prescribed regulations and, therefore, poses a potential health and safety risk to workers and members of the public, which is why the NNR has duly instructed West Wits to discontinue this unauthorised action with immediate effect,” he says.

At the heart of the problem are new water-management regulations released this year that direct mining companies to clean all pumped water to drinking-quality standard. 
Until now, they only partially treated pumped water before releasing it into the Vaal river system.

Until recently, DRDGold, Rand Uranium and Mintails treated 25-million litres of AMD daily at two plants.

But a stalemate in negotiations over water quality prompted Mintails to partially close its treatment plant in April, causing water in the basin to fill up.

Rand Uranium senior consultant for sustainable development Rex Zorab says that since the cessation of pumping and treatment by Mintails and DRDGold, the water level has risen.

Rand Uranium has been pumping and partially treating 13-million to 14-million litres of water a day.

Zorab says that the long-term resolve for the AMD problem in the western basin is the commissioning of the Western Utilities Corporation (WUC) plant to treat AMD to potable water level in February 2011.

Zorab notes that the WUC pilot plants that have been running since January 2008 have proved the economic viability of the ABC pro-cess supported by the Council for Scientific and Industrial Research, and the project is now in the bankable feasibility stage.

He adds that Rand Uranium has also done some testwork on an ion-exchange plant. 
“This is at a lower level of confidence at this stage, but is being pursued as a further option for different classes of water.

”

Zorab says that Rand Uranium has tested 
many other options over the years, but the focus has to be on sustainability, beyond the life of the mines and, currently, the most promising and advanced option is the Western Basin Environmental Corporation/WUC 
option, which offers a broader solution for the threatened discharges from the central and eastern basins.