The hazardous mining by-product raises two questions – who’s to blame and who should pay.
The acid mine drainage crisis is going to cost someone a lot of money, but probably not the people who caused it. The “polluter pays” principle was next to impossible to apply to the acid mine drainage problem in a retrospective way, said Marius Keet, chief director for mine water management at the department of water and sanitation.
“We have tried. According to our legal representative some years ago, it just was not possible.
“On which doors do you knock? Where do you go to? Who are these people?
“We all know that we have legacies inherited from the late 1800s,” said Keet.
“The idea is not to go back, the idea is to be more proactive in terms of what will happen in future,” he said this week at the launch of a booklet on mine rehabilitation by environmentalist Mariette Liefferink of the Federation for a Sustainable Environment.
Liefferink said the arguments against retrospective liability for acid mine drainage are overblown.
“There is a complete database of mines at the Council of Geoscience. The retrospectivity of the polluter-pays principle is an integral part of the National Water Management Act and the National Environmental Management Act. We would advocate for retrospectivity.”
Finding past polluters would also help the currently existing industry, she suggested.
“Most of the last-men-standing mines consider it unpalatable and inequitable that they should be liable for pollution caused over 150 years.”
In 2004, acid mine drainage started decanting out of old mines on the West Rand. Mines need to be constantly dewatered and, as mines have closed, pumping has ceased in many deep gold shafts, leaving them to get flooded. This water is highly acidic and dissolves hazardous metals, including the uranium that is a common by-product in Witwatersrand gold ore.
THE STATE OF PLAY
The agency implementing the short- and long-term acid mine drainage solutions is the Trans-Caledon Tunnel Authority.
It has three plants that pump acid mine drainage from the ground, partially treat it and discharge it into Gauteng’s river systems.
Between 150 and 200 megalitres of acid mine drainage water pass through these per day, costing just below R6 000 per megalitre, or roughly R1 million per day.
Partial treatment means adding lime to neutralise the water’s pH level. This makes most of the dangerous metals precipitate in a sludge that has to be disposed of. The resulting water is still contaminated with especially sulphates, but can be released into rivers.
“At least it is a lot better than what you can expect when you have it freely decanting,” said Keet.
Water levels in the central and eastern basins of the Witwatersrand are now falling instead of rising.
In the critical western basin, the rising water has at least been slowed down, said Keet.
“It has not stopped, but we’ve definitely reduced it.” The next step is to treat that water to a level where it can be sold to industrial and ultimately residential users.
“There needs to be a paradigm shift in South Africa about not being able to drink acid mine drainage. You can treat any quality water to any quality water, the cost is the issue,” said Keet.
The design of the long-term solution depended on who the buyers of the water ended up being, he said.
The long-term solution is meant to be operational by 2021 and the contractor to do an environmental impact assessment will “hopefully” be appointed within the next month, said Keet.
THE ECONOMICS OF ACID MINE DRAINAGE
Ideally, the long-term acid mine drainage solution should pay for itself by producing saleable water and possibly some mineral by-products. However, at current water prices, this is far-fetched.
The price to beat would be Rand Water’s tariff for water from the Vaal River – roughly R4.50 per kilolitre. That is more or less impossible, even with cheaper, new treatment technologies instead of the standard option – the electricityintensive desalination process called reverse osmosis. Mintek, the state’s science council for mineral processing, is punting a process it calls Savmin, which relies on a chemical reaction that uses less power. Mintek general manager Alan McKenzie said it can treat acid mine drainage at anything between R5 and R15 per kilolitre, “depending on the water you start with”.
A breakeven cost of roughly R20 per kilolitre is in the ballpark, but this is before any costs associated with disposing of the waste products or reticulation of the water to reach customers, said McKenzie. Johannesburg Water charges more than R30 to big water users, so, hypothetically, direct supply to a large industrial user could be cost competitive, he said.
“I don’t want to say water is too cheap now, but … somewhere in the future, where technologies improve and water gets more expensive, you could sell water and break even,” said Keet.
“The money has to come from somewhere and unfortunately, at the end of the day, it is probably going to be government. I just don’t see another way around it,” said McKenzie.
STOPPING THE DAMAGE
The department published a new mine water management policy paper last week that makes some far-reaching proposals – at least for the mines that remain. Among the proposals are restrictions on selling old mines to evade closure costs.
The problem of mines going into liquidation with no funding in place for rehabilitation is another target and an environmental levy on mines is being mooted.