JOHANNESBURG (miningweekly.com) – The Department of Water Affairs (DWA) has put out a request for information, inviting interested parties to propose a possible long-term solution to the management of acid mine drainage (AMD) in the Eastern, Western and Central basins of the Witwatersrand.

The department said the long-term solution would have to include the safe disposal, or use, of byproducts from the treatment of AMD, adding that the feasibility of such a solution would be increased by its inclusion of proposals for the removal of salts that were contaminating the nearby Vaal river and associated catchments, and suggestions on how to meet downstream user requirements and ensure security of supply.

Further, information regarding the design, construction, operation and maintenance of infrastructure, the use of waste products, as well as financing would have to be provided.

The DWA indicated that the proposed solution would have to be able to manage or treat the full flow of AMD expected from the basins, although proposals that put forward operating in modules of 10 Mℓ/d would be of interest.

It was expected that an average of 23 Mℓ/d of AMD would be extracted from the Western basin, 46 Mℓ/d from the Central basin and 80 Mℓ/d from the Eastern basin.

Information regarding proposed solutions would be captured for consideration in the ongoing feasibility study that was initiated in January 2012, aimed at investigating the most sufficient long-term solution to the AMD situation in the Witwatersrand and would also be used to inform the anticipated procurement of such a solution.

Interested parties had until January 31 to submit their registration forms and proposals on the DWA’s website.

BACKGROUND

The Witwatersrand basins are the main focus of South Africa’s AMD treatment needs currently and were elevated to a political level about two years ago.

Cabinet approved recommendations to deal with AMD in the Witwatersrand in February 2011, after which the Trans-Caledon Tunnel Authority (TCTA) was appointed to tackle the problem.

Last year, DWA water-quality management senior manager Marius Keet said at a parliamentary meeting that the Central basin’s water level below surface was at 334 m, while the environmental critical level (ECL) was estimated at 174 m below surface.

The TCTA has implemented an immediate solution, which has resulted in decant in the Western basin being stopped and the water being drawn down to 1 m below surface level; however, it is still far above the ECL, which is 150 m below surface.

In December, South African gold miner DRDGold announced that its surface gold tailings retreatment company Ergo had entered into a heads of agreements with TCTA for the construction of AMD pumping and treatment facilities in the Central basin.

London-listed Central Rand Gold (CRG) also said it would sign a memorandum of understanding with the TCTA on dewatering the Central basin, which would see CRG donating its Ritz pumps towards the AMD mitigation project.

TCTA concluded a third agreement wherein it awarded a R319-million contract to JSE-listed Group Five for the construction of treatment works and monitoring shafts in the Central basin.

Meanwhile, as a result of financial constraints, the DWA decided to postpone the treatment of the AMD from the Eastern Basin to a later stage, as its situation was less critical.

However, Keet indicated that the water was at 560 m below surface level in the Eastern Basin and estimated that the ECL, which was at 290 m below surface, could be reached by 2014/15 if no measures were taken.