Nanotechnology to curb water pollution in mining

acid mine drainage, Mining Indaba, Dow Chemicals The mining industry has also become far more water conscious and has begun using water-recovery technology on an industrial scale (Image: Brand SA)

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Sulaiman Philip

The problem of acid water draining from abandoned mine dumps and shafts has long seemed insurmountable, with some estimates putting the pollution on the Witwatersrand as high as 350 million litres a day. New technology from Dow Sub-Saharan Africa is finally offering a solution.

South Africa is the most industrialised and diverse economy in Africa, wealth built on mining. But while mining’s contribution to South Africa’s GDP has fallen, the industrial base built up around the industry has diversified and strengthened.

The historical importance of mining has created not just legacy issues – the ecological disaster of acid mine drainage – but has also strained the country’s water supply. South Africa is a water-scarce country, with its limited resources having to be shared between domestic and industrial – agriculture, mining, power generation – users.

Mining techniques have evolved since diamonds were discovered in 1867. There are no canaries in the coal mines and improved ventilation and extraction techniques have made South African mining among the safest in the world. The mining industry has also become far more water conscious and, with the help of companies like Dow Chemicals, has begun using water-recovery technology on an industrial scale.

Ross McLean, president of Dow Sub-Saharan Africa, says the web of industries in South Africa makes it possible for the company to provide clients with synchronised services.

“Power stations need a certain purity of water in the steam turbines. Today, you can set them up with a supply of recycled water from a mine – we have this kind of system in place in a power station in South Africa. We’ve helped with our technology for the purification of waste water from the mine to a standard where that recycled water can be used in the power station. This creates a green linkage from mining to energy, which of course is a critical sector.”

Nanotechnology for water filtration

Dow’s world-leading reverse osmosis, nano-filtration membranes and ion-exchange resins allows industry to optimise water management. For McLean the future of mining has to be about sustainability, and water management using Dow technology should be at the forefront of any decisions made about operations.  

Karen Dobson, Dow’s global business director for mining, adds that the technology has the benefit of being able to, dependent on the system used, produce safe water with zero discharge.  She says Dow technology can play a greater role in removing heavy metals from aqueous tailing discharges. It also has value in the secondary recovery of valuable metals from tailings and waste streams, helping reduce mining’s environmental impact.

“The environment and social pressures are becoming more challenging for the mining industry. These are some of the very problems and challenges facing the industry we believe we can contribute to providing sustainable solutions.”

More than a century of mining has left South Africa with mountains of waste – tailings dumps – and networks of abandoned shafts. Shafts on the Witwatersrand are veined with pyrite – an iron sulphide known as “fool’s gold” because of its superficial lustre – which reacts with rainwater and groundwater to decompose into sulphuric acid.

Pollution in major water sources

Geologists estimate that acid drainage from abandoned mines on the Witwatersrand could reach 350-million litres per day. This is untreated water that flows into the watershed of the Vaal and Limpopo Rivers, which supply water to millions of people

In 2013 the government budgeted R150-million to deal with acid mine drainage. With 6 000 derelict mines in the country, the World Wide Fund for Nature estimates that South Africa would need to spend R30-billion to solve the problem. “The longer we wait to address this issue, the more it is going to cost the South African taxpayer in the long term,” Deon Nel, head of the WWF’s biodiversity division, told the Mercury in 2013.

Dow has been actively marketing its nano- and ultra-filtration membranes as solutions to the legacy problems of the mining industry. Not only can the technology remove harmful components from tailing waters, but it has given birth to a secondary industry recovering valuable metals from tailings and waste streams. It can reclaim metals that were otherwise too expensive to recover while reducing the environmental damage done by mine dumps and abandoned shafts.

For Dow, investing in technologies that solve problems like acid mine drainage is an investment in the future of the company. “Business will not be sustainable if we do not get that right,” says McLean.

“Our solutions, especially in the mining space, can help deal with the legacy issues that remain after operations cease. Sustainability is at the core of how Dow does business. Not just in terms of how we manufacture products but how we take those products to our customers. It is a philosophy that we share with our customers who are looking to adopt best practice around sustainability.”

RossMcLeanPicJan15 According to Ross McLean an investment in sustainable technology is an investment in future succes. (Image: Dow Chemicals)

Investing in Africa

On average, the African economy is predicted to grow between 6% and 7% over the next two decades. Despite the forecast growth, just $3 of every $1 000 invested by American companies goes into Africa. For most investors Africa is still the dark continent of terrible headlines.

But for companies already on the ground in Africa, like Dow, the continent is a thriving marketplace. Dow brings 117 years of expertise to a region with diverse needs and almost unlimited growth potential.

 In terms of Dow’s global business, sub-Saharan Africa is a relatively small market but, McLean argues, that market will grow more important as Africa industrialises. “In South Africa you would not say industrialisation, you would say it’s a drive to re-industrialisation – which the government is pushing. We see this market as really interesting because of its level of diversification plays to the variety of solutions we offer.”

Dow is expanding in Africa, with offices in Egypt, Ghana, Nigeria, Morocco and Ethiopia.  McLean stresses that it remains a business-to-business company, one that touches most industries in sub-Saharan Africa. The level of diversification in African industry plays to Dow’s strengths and the solutions it can offer as well, McLean says.

“Our investment is about putting more people on the ground to bring our technologies to our customers. We have been investing in chemistry, science and technology for 117 years. Deeply embedded in our history is a lot of know-how and technology. We have already invested a lot in the [environmentally sound] solutions and technologies that African industry needs.”

McLean admits that each country in which Dow operates in has its unique problems, but the rewards of working in Africa are infinite. “There are some really interesting challenges. But the thing is, companies like us go after opportunities when the opportunity is big enough to warrant the risk. It’s a risk-reward balance; there is no question we see the opportunity for growth. I think we are succeeding.”

Dow’s African strategy is the result of eight years of research on business conditions in Africa. And while it conforms to local conditions, the company has adopted a “be local but act global” approach to business. It has created systems to develop African talent and leadership, people who are then immersed in the culture of Dow.

“We understand that large multinationals like us can’t really understand African markets until they have feet on the ground. Is Africa challenging?  Yes. You really have to adapt to the situation in each country. You almost need a manual on how to do business in Nigeria, Ghana, Ethiopia and South Africa.

“Saying that, we do not compromise our standards around health, safety and the environment in Africa,” says McLean.

“It would be far more expensive if we did not maintain our standards and got it wrong.  There are costs associated with doing it right, but we absolutely do not compromise. We’d sooner not do the business than break our own rules. If we businesses get that right, they will succeed in Africa.”

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