MechChem Africa

At the SAIChE annual dinner for the Gauteng branch, Mariette Liefferink, CEO of the Federation for a Sustainable Environment (FSE), delivered this keynote address on acid mine drainage (AMD) and the state of South Africa’s water resources.

AMD Sludge deposits Mariette Liefferink FSELiefferink’s first slide shows that, in terms of water availability in South Africa, 12 of our 19 Water Management Areas (WMAs) require intervention, with the requirements exceeding or very close to exceeding total water availability. For South Africa as a whole, our current requirement is already perilously close the 14 000 million m3/annum currently available to us.

By 2025, all four international river basins – the Orange, the Limpopo, the Incomati and the Maputo – will move into absolute water scarcity leading to economic stagnation and potential social decay. This before taking climate change into account.

The Limpopo River Basin is already over-allocated by about 120% and is facing a 241% increase in demand by 2015, Liefferink says, referencing a 2009 study by Ashton.

She cites some reasons for the dramatic increase in water demand in the region, which include: current and proposed mining activities; Sasol’s proposed Mafuta coal-to-liquid fuel projects; the exploitation of the vast coal reserves in the Waterberg; the expansion of the Grootegeluk coal mine to supply the Medupi Power Station; Medupi, Kusile and proposed new Eskom power stations; and the implementation of the Ecological Reserve, which is expected to result in serious deficits in some of the main river catchments.

Touching on the DWS’ 2014 Reconciliation Strategy for the Orange River, she points out that supply and demand are currently at the crossover point. While intervention is required immediately, the situation will not improve before the Polihali dam is completed in around 2023 – and this will only achieve in temporary relief.

As well as growing water shortages, however, the salinity in the Orange River is increasing alarmingly because current AMD treatment strategies involve neutralisation only, which results in water containing dissolved salts being discharged into the river.

Mining and AMD

There is wide acceptance that acid mine drainage (AMD) is responsible for the most costly environmental and socio-economic impacts. AMD is a long recognised problem within the gold mining industry: it was referred to as an established phenomenon concerning pumped water on the Witwatersrand back in 1903.

AMD has a low pH and high acidity, but in addition to the acidity of AMD minewater, a number of other elements/determinants are also present in the water, mostly metals. Many of these are present in toxic concentrations in the water. Radioactive metals also occur in the water.

AMD, says Liefferink, is associated with surface and groundwater pollution; degradation of soil quality; for harming aquatic sediments and fauna; and for allowing metals to seep into the environment. Long-term exposure to AMD-polluted drinking water may lead to increased rates of cancer; decreased cognitive function; and the appearance of skin lesions.

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