Time for AMD debates has run out - SA must act now!
The issue of mine water treatment and management has become urgent for South Africa. It was always important, but now we have run out of time to debate and must act, says the Water Research Commission Research Manager Dr Jo Burgess who currently serves on the InterGovernmental Task Team on Acid Mine Drainage (AMD) .
Ownerless mines which have become wards of the state are more vulnerable to releasing untreated water to the environment. Nothing has been done yet treatment is still required there. The impacts of uncontrolled decant (emergence in subsurface and surface environments) of some types of mine water are severe. Many types of waters exiting mine workings are not acidic; neutral mine water is almost harmless (depending on what has dissolved in the water). However, at sites where mine water is acidic (with a pH below 6; mine water with pH of 6 - 8 is classified as NMD, neutral mine drainage) have been escaping into the environment without control suffer severe damage when acidic water, dissolved metals and salts get into rivers or lakes or re-enter downstream aquifers. The salts and metals can be toxic to plants, animals, and people.
Dr Burgess confirms that in South Africa mine water treatment already takes place at several sites. However, every site is unique, because the amount of water that needs to be treated, the characteristics of the water to be treated and the characteristics of the desired resulting water all influence what treatment is needed. For example, saline drainage needs a completely different treatment process to acid mine drainage. Mine sites which are still active include mine water treatment which is done by the mine owners like the water reclamation plants in Mpumalanga, operated by Anglo Coal and Optimum.
According to Burgess the current hindrances to effective treatment of AMD are mostly not scientific or technical in nature, but relate to institutional arrangements and funding. Over 20 different methods of treating all the types of mine waters have been developed worldwide, so the issue isn’t that people do not know how to treat the water. Most of the factors come from problems identifying who should be responsible for paying for or effecting the treatment, and deciding what type of water we want to produce by treating AMD. For example, it is possible to treat water to different extents so that it is suitable for industrial use, or for irrigation of certain crops, or for release into rivers, or even for drinking. The other issue is where the treated water and the by-products of treatment will be sent. The by-products are created because AMD is basically water with things dissolved in it; when you take those things out to create clean water, you are left with the same things and have to do something with them.
“We need to align the regulatory functions of the Departments of Water Affairs, Environmental Affairs and Mineral Resources that relate to mine water and create a regulatory environment that enables the private and public stakeholders to work together in implementing the treatment methods that we already know about,” comments Burgess.
It should also be noted that there is no one single treatment process that can be used for all sites with AMD; each site must have a tailored treatment process created for it. There are four types of different treatment methods, categorised according to what you want to achieve using the selected method: (1) neutralisation, (2) metals removal, (3) desalination, and (4) specific target pollutant treatment.
The way in which treatment of mine water must be done is selected on the basis of the quality and quantity of untreated water and the desired treated water quality. Also, water treatment is usually only possible using a combination of treatment processes. Each process is called a ‘unit operation’ and several unit operations are put together to tailor-make a ‘process train’ for each individual situation. For example, if the water is acidic and contains heavy metals, then treatment technologies would be selected from the lists for neutralisation and for metals removal, and placed in series in the process train so that all the pollutants in the water are removed.
South Africa does not lack knowledge, since methods of dealing with AMD do not differ from those used in other parts of the world, adds Burgess. The international gold standard for dealing with AMD is a document called ‘The GARD Guide’ - GARD stands for Global Acid Rock Drainage - and Acid Rock Drainage, or ARD, is the most commonly used term internationally for mine water. The GARD Guide actually includes treatment of ARD, NMD (neutral mine drainage) and SD (saline drainage), and the guide was created through the contributions of many individuals and organisations around the world, including several South African organisations.
It is high time that we allow partnerships to be created. No single stakeholder has all the answers and resources needed for a complete solution to the problem, concludes Burgess.
Contact :Dr Jo Burgess, Research Manager, Mine Water Treatment and Management