Sinking Solutions for Mining Water Pollution in South Africa’s largest city, Johannesburg. It faces the looming threat of toxic water spewing out of idle mines as early as next year, unless government steps in to prevent an “environmental disaster”, Terence McCarthy, professor of geology at the University of Witwatersrand”. In a report entitled “The decanting of acid mine drainage in the Gauteng city-region”, McCarthy said government should bear the costs of dealing with the acid mine drainage (AMD) problem – the toxic water trapped in the mine void in the Witwatersrand, which stretches from Roodepoort to Boksburg. Most mines in this region are no longer operational. AMD occurs due to the outflow of acidic and heavy metals-laden water from Witwatersrand-based mines, which threatens to pollute surface and ground water.
According to his findings, McCarthy said in 2011, possibly 2012, AMD will seep up through the main shaft at Gold Reef City, and this underground facility will be forced to shut down. Boksburg, he warned, could see acid mine drainage rising up through drainage points, spewing toxic filth into the town.
The geologist said the mine void, a large hole left after decades of mining, will have filled and underground water carrying sulphuric acid, heavy metals and a number of other toxins will spill out and could compromise “our cities and towns, our economy and environment, our reputation, and arguably, our future”. McCarthy said the Department of Water Affairs last year indicated that AMD from abandoned mines could result in catastrophic ground and surface water pollution.
Already, the Western Basin of the Witwatersrand is decanting, meaning that acidic and heavy-metals-laden water from the mines is now spewing into rivers and the surrounding environment. Environmental activist Mariette Liefferink warned this week that AMD is not only associated with surface and ground water pollution and degradation of soil quality, it also harms aquatic sediments and fauna and allows heavy metals to seep into the environment.
Derek Watts (Carte Blanche presenter): “Since our last story the mine water crisis across Johannesburg has been headline news around the world. The government appointed a technical task team which has reported back to the ministers involved.” They compiled this report, released last week in which they outlined suggestions to fix the problem in the short term.
Edna Molewa is the new minister of water affairs. Edna Molewa (Minister, Department of Water Affairs): “One of the things that the team suggested is that we should begin with the area around Krugersdorp where the problem is very bad right now. And that’s a decision right now that stands; there is money provided for that programme.”And after a long stalemate government have finally agreed to pick up the tab to pump and partially treat the water. Edna: “Right now there is almost a R400-million cost estimation. We do know that the amount needed is going to be close to a billion… thereabout. And that is not the end.”
Prof McCarthy: “What the recommendations are is to return the situation to the status quo as it was in the case of the Central basin to 2008, in the case of the Western basin to 2002, and in the case of the Eastrand basin, what it was before Grootvlei stopped pumping. So that will involve pumping and basic treatment, which involved precipitation of the iron in the heavy metals with the addition of lime and oxygen, and then the release of the sulphate rich water into the rivers.” But pumping is only half the story. Water is so toxic it needs to be treated properly before its released into the rivers and that is where the proposed solution falls short. The team proposed that government neutralise the water. What that means is that lime is added. That attracts the heavy metal particles to settle to the bottom as a toxic sludge. Around 100 000 tonnes per year of this sludge will need to find a home in pits. The rest of the water is released into rivers but still contains salt or sulphate levels way beyond any international or locally acceptable levels. Prof McCarthy: “It’s not a long term solution because you need high quality water to dilute but you also need to use that high quality for consumers. So you are caught between a rock and a hard place: you have to throw away good water simply to improve the quality of bad water and that is an enormous waste.” Already a million tonnes of sulphates per year are going into the Vaal barrage. Clean water from the Vaal Dam is released simply to dilute the water so it can be cleaned up for drinking downstream. High salts means your water costs could double.
Prof McCarthy: “So in order to provide additional water to allow for the dilution they will have to bring on the Lesotho Highlands scheme earlier. If you can take the salts out or prevent them getting in then obviously you save water.” So surely then salt removal should be at the heart of any solution?
We took a look at three different solutions to see what is on offer. Physicist Richard Doyle says their solution is zero waste as it removes all the salts. Richard Doyle (Managing Director: Earth): “The water problem, the mine effluent problem is not a water problem it’s a salt problem. All of the technologies can manage – or many of them can produce clean water. What differentiates us is that we can usefully employ the salts and that is critical.” Richard: “So here is a tin of soup – imagine this comes in the front of the plant. Here’s our pilot plant – it is a small version of what we’d eventually build – and the easiest way to think about it is that on this side we’ve got this type of vegetables: carrots, let’s say, yellow vegetables. These are typically the metals like uranium, calcium and magnesium and iron and aluminium. And in here we’ve got little resin beads, but these are like rabbits, they grab the carrots because they like them. What comes out of there is the vegetable soup, but it only has peppers in it. And here we’ve got donkeys that like the peppers and they grab the peppers. So we take the carrots out there and the peppers out here and what you see is just drinking water; we’ve completely cleaned the water.” Richard contends that his process will be funded by the sale of the by-products; selling the water would be a bonus. Richard: That means we will enter into an off-take agreement with the mine – they will give us their junk, we will raise money and build a business around that, and it is a great story.”
In Randfontein is the pilot plant of the WUC process which was the forerunner in the big clean up.” Jaco Schoeman is the CEO of the Western Utilities Corporation. Their plan is to pump the water from each basin to a central treatment station. This pilot plant is a miniature version of a proposed 14 hectare plant costing about R1.5-billion. WUC uses a solution developed by the CSIR called the Alkali Barium Calcium process to clean the water. Jaco Schoeman (MD & CEO: Western Utilities Corporation): “What you see here today is just the technology – there are five specific legs to the solution.” Jaco has spent 4 years and R75-mllion rand in the hope that government will accept their pumping and treatment proposal. But they have faced a barrage of criticism because the only way they could fund it was to sell 100 million litres per day onto Rand Water at a profit. The WUC process was also the mining industry’s answer to the problem. Jaco: “When we presented this plan to government it was perceived that we were trying to privatise water, which is against the Constitution. That was obviously not the intention – we were tasked to find a long term self-sustainable solution for the mining houses. We are prepared to do this entire project open book in terms of operating cpst and capital cost.” Four mines send their toxic water here to Anglo’s Emalahleni plant in Mpumalanga. According to Terence the water around the town is so polluted in some cases it’s unusable. Prof McCarthy: “The power stations in the Witbank and Middleburg area cannot use the water for power generation. The salt level in the local rivers in the Middleburg area is so high now from coal mining that they can’t use it. They have to import water from the Usuthu and Komati rivers.”
Back in 1995 the water was corroding the pipes at Anglo’s mines so quickly that hydrologist Peter Gunther started researching different clean up solutions. Peter Gunther (Regional Manager, Hydrology: Anglo American Thermal Coal): “There was a water issue – the plant was corroding away and we needed somebody to look at water. So as a challenge I took it up.”The result is this R500-million plant that has won awards for its innovation and is sending high quality water to Emalahleni residents.
When you look at the water as it comes through initially, it looks like a lost cause. But Peter states that Reverse osmosis technology has the ability to remove anything from water. And with the mine water that they have got they know they can make good quality potable drinking water.”
The way it works is that the water comes in from the four different mines like this. The water is then pre-treated using lime and limestone to neutralise the acidic water. The solids are separated out into these enormous tanks and then the water is taken through a three stage desalination process to remove the salt from the water. The plant is expanding and will soon release no salt water as waste. The downside is its expensive and in effect they make a loss on the water they sell. R11 per kilolitre is the right amount at the moment, but the focus was going for zero waste will help our costs over time.” And they are turning their waste into houses. One of the ideas that they came up with was instead of just disposing of the waste for eternity is what can we do? Gypum and housing are synonymous with one other so we have now built 66 houses out of Gypsum.”
Houses, explosives, fertiliser – South Africans have found innovative ways to turn the toxic tide into an opportunity and create jobs at the same time. We could turn our acid mine drainage problem into an opportunity but do our leaders have the vision?