As acid mine drainage threatens some of South Africa's major cities and waterways, technology providers are looking for cost-effective solutions.
With acid mine drainage (AMD) threatening some of South Africa’s major cities, waterways and industries, South African technology providers are getting on the solutions bandwagon in the hopes of providing a novel approach to cleaning up an overwhelming mass of polluted water.
There are many methods already available or in the pipeline, ranging from using microbes to building faux-wetlands to ion exchange in order to remove sulphur, heavy metals, and increase pH, allowing water to be discharged and/or used for human consumption.
While their effectiveness varies, one common thread runs through: they all take time, money and commitment-qualities that both often wanting from the mining industry and government.
Companies are also accused of being opportunistic, trying to make a buck out of a environmental nightmare: as water simultaneously becomes a scarcer but more heavily demanded commodity, water treatment is seen as a greater economic opportunity for companies looking for new markets to tap into.
Still, scientists and activists defend companies’ ability to make money out of treatment, claiming that if they aren’t allowed to at least break even, there will be no incentive to clean a massive liability, which will then be shouldered onto the state.
Below are some of the treatment options being championed across the country. For more on solutions to AMD, please see how to fix an impossible mess
Wetlands: mimicking nature’s passive treatment
The so-called wetlands approach was stumbled upon by American scientists in the 1970s, who noticed that some of the country’s AMD was being partially treated when the polluted water ran through natural wetlands, resulting in heavy metals being removed and the acidity decreasing. Interested in harnessing the natural technology, Ronald Cohen and his colleagues at America’s Colorado School of Mines simulated wetlands, pin-pointing naturally forming bacteria named sulfate-reducing bacteria, or SRB. Research was done worldwide, with some of the major testing facilities housed in South Africa.
These faux-wetlands, also called bioreactors, can remove some of the contamination, but not all, and not in large quantities. “[They] can treat very high levels of metals, and bring them down to very low levels, in some cases almost near zero, but that’s only with very small flows,” explains Cohen. “If you want really good treatment, simply using one of these bio-reactors is not going to do a very good job. They can be part of a solution, but generally not a total solution.” Yet while their effectiveness is limited, their cost is also reduced. “You can operate them without any power — you don’t need great holding tanks operating 24 hours a day with people there all the time, you don’t need gigantic chemical deliveries or large amounts of lime [used to neutralise pH],” he said. “The capital cost of constructing these systems is much reduced. Operation and maintenance may mean that you need to have somebody come out once a week, but that’s it.”
But while the wetlands approach has been used extensively in the United States and the United Kingdom, applying it to the South African environment may not be appropriate, given the large amount of water to be treated and highly-contaminated nature of the water. According to Koos Pretorius, a Mpumalanga farmer and director of the Federation for a Sustainable Environment, “we have too much water for a passive system. They use them in the UK, where they have much smaller amounts of water and low sulphur rates. We’ve got high volumes of water with high sulphur rates.” In the West Rand of Gauteng alone, up to 30 ML, or 30 million litres, of water daily floods from filled mine voids, with hundreds of millions litres more predicted to be generated within the coming years.
Harma Greben, senior scientist at the Council of Scientific and Industrial Research (CSIR), notes that a passive treatment like a wetlands system takes much longer than more technical and expensive active treatment. “With the passive treatment — at least 20 days is required, whereas with active treatment, the same volume of water can be treated in about one day — [Passive treatment] — can be applied to lower volumes of AMD — With a functioning mining operation, producing vast volumes of AMD, it’s not recommended to apply a passive treatment system.”
The use of microbes as a naturally occurring cleaning product is being piloted by the CSIR. “Biological treatment means that you use microorganisms to clean the water, but only the organics and nutrients, such a sulphates, nitrates and phosphates can be eliminated,” explains Greben, who has been working on biological treatment at the Council since 1986.
While the work has proven to be significant in reducing sulfate content within a lab setting, it has yet to be done on a larger scale. Initial work has reduced sulphate levels to less than 100 parts per million (ppm), far below the 500 ppm level required by the Department of Water Affairs (DWA) before water can be released into the natural environment. As the sulphate level drops and the pH rises, a side effect of the carbon source used in the process, heavy metals also precipitate.
“We can make this water usable again,” says Greben, who notes that while the water can be used for agricultural use and discharged into rivers and dams, it still is not fit for drinking purposes. “This water could eventually be used for drinking water, but it would just need the normal process of what Rand Water does to its water. If you can treat such polluted water to levels that it can go back to the river, then there’s nothing wrong with it.” AMD can be cleaned through the process within two days.
While exact cost models have yet to be put together, Greben notes that the biological process is likely to be much less expensive than the more technologically intensive chemical and physical processes. “You don’t need any chemicals,” she explains. “All you need — is a carbon source, because in order for the bacteria to do their job they need to eat — they need carbon to sustain.” Additionally, the process produces no chemical waste, and technologies exist to retrieve valuable heavy metals such as copper and zinc after metal sulfide precipitation.
The Aveng Group
Aveng has garnered significant media coverage over its work in partnership with Anglo Coal, BHP Billiton, and Optimum Coal, cleaning millions of litres of the coal companies’ AMD to potable standards. In 2008 the group acquired the company Keyplan, which has been treating AMD for over 20 years through reverse osmosis. The process increases the pH, allowing for sulphur and heavy metals to precipitate, further cleansing the water by pushing it through a series of membranes, and finally employing the company’s HiPRO process, or high recovery desalination process. The company claims this process “significantly outperforms any comparable technology with its ultra high water recovery”.
According to Anglo Coal South Africa manager Peter Gunther, while the company first commissioned Keyplan to treat its AMD in 2002 in order to salvage their own operation and because of environmental concerns, “it’s not just about doing the right thing anymore. It goes beyond compliance. We’ve seen — strengthening of relationships with different stakeholders be it other mining companies, regulators, [and] the local government.”
Vik Cogho, group health safety and environmental manager for Optimum Coal, notes that as treatment technologies are fine-tuned, less waste will be created, bringing down the cost of treatment. “There’s a lot of research going on [regarding] mine water treatment and especially brine sludge streams, which is actually quite an expensive component — We feel we will be able to end up in a zero effluent situation, where we don’t generate waste anymore,” says Cogho. Waste disposal facilities account for 20-25% of the capital development cost and have a limited lifespan, meaning that under normal circumstances they have to be extended every 4-5 years at a significant cost. “Indications are that Optimum Coal will probably never have to construct additional waste disposal facilities again.” Aveng hopes that 100% recovery will soon be achieved, with no waste being produced.
“Technology improves day by day,” continues Cogho. “We’re only looking up. To date some government and industry players have been seeing this as primarily a negative thing, but you need to focus positively on this. There’s a lot of opportunity within this as well.”
The Western Utilities Corporation
The Western Basin Environmental Group (WBEC), a section 21 company, was formed in 2006 by several mine houses situated in the Witwatersrand in response to the government’s insistence that industry take a larger role in responding to AMD before receiving coveted closure certificates from the Department of Mineral Resources (DMR). WBEC tasked the Western Utilities Corporation with finding a technology that could treat their collective water. After testing several different potential technologies, WUC settled on the ABC process created by the CSIR. The process focuses on either recycling or utilising waste stemming from lime treatment, the most common and cheapest type of treatment, so that the process can be both cost effective and as waste free as possible. Through their GypSLiM process, assets such as calcium carbonate, magnesium carbonate, sulphur, and heavy metals can be removed and re-packaged as economically viable products.
Marinda de Beer of the CSIR explains the creation of ABC. “The process evolved over many, many years. First we had to deal with acid by raising the pH, and then we realised in doing so, [waste] was a problem,” she says. “[The ABC process] is a chemical precipitation process where the sludges you produce, you convert back into re-agents or valuable products. There’s as little waste as possible.” The technology has only been used at a pilot plant through WUC, treating 1 000 litres daily.
While many critics contend that the ABC process is both ineffective and too expensive, pointing to problems in the pilot project, de Beer says that CSIR “aims for 100% recovery” and that many improvements have been done mainly to reduce cost. “At the end of the day, people don’t want to put money into — treating waste. We’re working on getting the cost down, although I think this is the cheapest of all the technology currently.” The treated water could be discharged or used in agriculture, but would still need to go through a more thorough treatment process, like that of Rand Water, in order to be drinkable.
While WUC currently uses the ABC process, Schoeman says that the company differs from its competitors in that it is not pushing for a singular technology, and is open to using whatever solution works best for the lowest price. “[WUC doesn’t] own the technology, so [we] don’t care what technology we implement,” he says. “If you dictate to me to use reverse osmosis, it’s fine, but then the cost is going to be four times.” WUC proposes to pump water from all of Gauteng’s affected basins to a central treatment station, claiming that it’s more economically and logistically viable to treat from one plant than several smaller ones. At full capacity, WUC would treat 300 ML/day.
Earth Metallurgic Solutions
Earth is the new kid on the block. In 2007, three friends with backgrounds in science and business came together to work on treating and extracting valuable products from mine waste, including acid mine drainage.
By using filters and ion exchange, Earth claims that its treatment process is waste-free, with all pollutants being removed from the fluid. “If you’re not squishing stuff together or adding other chemicals in, which other approaches invariably do, then you have a flexibility, you pull each and every one of the elements out, and then you do something with that,” says managing director Richard Doyle. The company has made potable water, fertiliser, explosives, and concentrated solar power salts from AMD, in addition to removing valuable heavy metals such as uranium. Earth successfully piloted its treatment process at five mines over the last year, and believes it will be building their first commercial plant within the coming months.
It’s been an uphill battle for the company, who are struggling against larger and more established companies like Aveng. “It’s very difficult to make progress in this game unless you have agreements with the mines,” says Doyle. While the company is in “continual talks” with government, “their position generally is that it’s not their role to choose technologies or tell the mines what to do”.
Doyle claims that different industry players must work together and with government in order for AMD to be comprehensively addressed. “We — emphasise the need to back a range of South African and other technologies,” he says. “This is not the first time people have tried to solve this technology in South Africa, and there are several water treatment plants or previous efforts that have fallen over in the past because they didn’t work, because times change, because they’re too expensive. You need to run a range of different technologies for a long time — we have to all work together to try and solve the bigger problem.”
Shifting our legal and political environment
In addition to creating effective scientific solutions to AMD, activists and policy analysts claim that a major political and legal shift needs to occur in order for mine waste to be adequately addressed. “The problem isn’t that we don’t have the technology, it’s that it’s not being employed,” says Democratic Alliance MP Gareth Morgan. “There are stacks of mines which are operational currently, so the government has to make sure that the existing mines have proper and enforceable closure policies, that the mines have to pay for the damage that they have done. The other part of it is as important: this country has to have an honest debate about where mining as an activity is appropriate and where it is not.”
Mariette Liefferink, CEO of the Federation for a Sustainable Environment, says that lack of discussions around the true cost of mining, including AMD, allows for the problem to continue without being properly acknowledged. “Acid mine drainage is not a unique South African problem. What is unique — is that it is denied, it is suppressed, it minimised — and not addressed,” she says. Melissa Fourie, executive director of the Centre for Environmental Rights, agrees. “I think the response has been small because government officials are paralysed by the enormity of the problem. The big things like liability have been difficult to deal with. It’s difficult to change the status quo, it’s difficult to challenge the mining companies. But it has to be done.”
Legal experts note that overlapping governmental roles and responsibilities make it easy for one department to shoulder the problem of AMD onto another, leading to a perpetual blame game. A CSIR note on AMD claims that roles and responsibilities of different government departments are “vaguely defined,” and that the government is “reactive rather than proactive.” Matthew Havinga, resident of Gauteng’s East Rand who lives on the banks of the polluted Blesbokspruit, has gone to both the DMR and DWA, receiving little support from either. “You have a situation where DMR and DWA sit almost in competition,” says Havinga. “DMR wants jobs and money, while the DWA are tasked with looking after the environment. Whether they take one another seriously or not is a huge challenge.” Morgan agrees. “The mining department has a mandate to promote mining, but they are doing it at the expense of our sustainability. They are externalising the costs of the mining industry onto the agricultural sector and the poor, effectively.”
Advocates claim that increased governmental leadership is essential to remediating polluted water. “Political will is what’s required to fix the problem, and it’s lacking,” says Morgan.
For more on AMD, visit www.mg.co.za/amd. This project was made possible by funding from the Open Society Foundation for South Africa’s Media Fellowship Programme