“The Vaal River reconciliation studies predict that there’s a water security risk in [the region] from 2016/17,” chief director Marius Keet, an AMD expert, told Parliament’s water affairs portfolio committee.
He emphasised this was a worst-case scenario only “if nothing is done”.
While infrastructure was in place to neutralise and remove metals from acid mine water — which started decanting from the western parts of the Witwatersrand gold mining basin in 2002 — the salts that remained in the discharged water, even after it was neutralised, posed a grave threat to river systems.
Keet said acid mine water in the Witwatersrand’s central and eastern basins had started rising after mining in the two areas stopped in 2008 and 2011 respectively.
The yield of the central basin was about 40 megalitres a day though this could go as high as 80Ml/day, while the yield of the eastern basin was between 80 and 110Ml/day. A megalitre is one million litres.
Keet said the neutralised water was being pumped to the Vaal Barrage.
“The challenge we sit with… is that once you release the water, even if it’s neutralised, it still has a high salinity. Because of that, you have to dilute the water downstream.”
This required between seven and 11 cubic metres of fresh water for every one cubic metre of high-salinity mine water discharged. Such fresh water had to be drawn from the upstream Vaal Dam.
“That is very expensive and unsustainable, and it’s water lost from the Vaal River system which has to do with water security.”
Keet noted that the department had a commitment to water users below the Vaal Barrage to keep the level of dissolved solids in the river below 600mg a litre.
According to notes tabled at the briefing, releasing huge volumes of mine water that has not been desalinated could have potentially catastrophic environmental and socio-economic impacts on the region below the Vaal Barrage.
Keet said a feasibility study had shown the long-term solution was to remove or suitably reduce salt load in the Vaal River system.
One way to do this was by reverse osmosis, a technology that involved passing the water through a membrane to remove the salts.
Keet said that to install a suitable system would cost an estimated R10billion.
“If we go… with neutralisation and desalination it’s going to cost us R10bn. If you don’t do it, you’re going to have to put in a new augmentation scheme which is going to cost the country R40bn. So it’s actually a no-brainer…”
Further, there was not enough water in the Vaal River system to keep on diluting.
“Desalination is something that has to be done because we can’t tolerate this [diluting the water] for longer than 2016/17,” he said.
A target date for commissioning a desalination scheme was 2016/17.
Stressing the urgency of the situation, Keet told MPs: “We still have time but the decision has to be made soon.”
He said the cost of neutralising and desalinating AMD had implications for Vaal River raw bulk water users, and consultations were being held with them.
The cost included a projected water increase of 23 cents a cubic metre in 2015/16, of 29 cents/m3 in 2016/17, and — once desalination started from 2017 onwards — a projected increase of 99 cents/m3.
According to the department, a new pump station on the central basin, at Germiston, commissioned in April this year, is currently neutralising and discharging 56Ml of AMD a day.
A similar pump scheme on the eastern basin, at Grootvlei Mine, is set to come into operation in December next year. It will be able to neutralise and pump 84Ml of AMD a day.
Pumping is necessary to stop the rising AMD reaching environmentally critical levels.
Speaking at Wednesday’s briefing, Chamber of Mines senior executive Nikisi Lesufi told MPs that in many countries the state took responsibility for AMD.
“Our regulatory framework has not provided for the establishment of an institution or a structure that will essentially look at the legacies of mining.
“Because whether we like it or not, the country did benefit from the historical practises of mining.”
He called for co-operation between the mining sector and government to tackle the problems of AMD.