JOHANNESBURG (miningweekly.com) – There is sufficient dilution capacity to ameliorate the untreated acid mine drainage (AMD) and neutralised AMD decanting from basins in the Witwatersrand between now and the end of 2014, Water and Environmental Affairs Minister Edna Molewa said on Tuesday.

In response to a Parliamentary question posed by the Democratic Alliance’s Gareth Morgan, the Minister stated that untreated AMD flowing north into the Crocodile catchment in the Witwatersrand’s Western basin region was being diluted by partially-treated mine water and other water sources such as springs and tributaries of the Crocodile river.

Molewa said following dilution, water quality monitoring in the Crocodile catchment showed significant improvement.

She added that the short-term plan for treating the AMD in the Witwatersrand took into account the impact of residual sulphate in the treated mine water and that dilution released from the Vaal river system would be required to ensure that the sulphate level in the water was maintained to be fit for downstream users.

Current Vaal river system water quality and quantity modelling showed that demand on the system permitted the release of fresh water for this purpose.

However, Molewa stressed that as part of the Vaal reconciliation strategy, all salt loading, including the discharge of the neutralised AMD in the Vaal system should be discontinued by 2014.

“It is accepted that the discharge of the neutralised AMD containing high residual sulphate levels into the Vaal river system is not sustainable. For this reason, the short-term treatment of the AMD will only operate as an emergency intervention to treat the current decant of the AMD in the Western basin and prevent decant in the eastern and central areas,” she assured.

The Minister further said the long-term study on the mine water management in the Witwatersrand was under way and that it would take into account all factors for the development of a solution towards the sustainable management of the AMD.

However, Morgan told Mining Weekly Online that the interim solution to treating AMD was not satisfactory, as sulphate levels would remain high in the discharge into the Vaal river system, while risks could be mitigated by diluting it further.

“Precious clean water is still being wasted,” he warned.

Molewa will on Thursday provide an update on progress being made in dealing with AMD in the Western basin.