Science, Technology and Engineering

Environmental Geoscience

Research Programs

Acid Mine Drainage

Acid mine drainage (AMD) is generated when sulphide minerals, usually exposed by mining, are exposed to the atmosphere and oxidise, releasing acidity and dissolved heavy metals. AMD must be neutralised before it can leave a site, and this process generates a sludge which has to be disposed of. Research at La Trobe University on AMD has concentrated on 2 aspects:

Increasing the chemical stability (resistance to leaching) of neutralisation sludges

Danny McDonald's PhD project (2006) showed that the sludges are readily leached by acid waters, no matter which chemical is used to neutralise the acidity, and should not be disposed of in pit lakes. He also demonstrated that if the iron minerals in the sludge are crystalline, they are much more resistant to acid attack. This project has proceeded in cooperation with several environmental consulting companies, particularly Earth Systems and URS, and has also received financial support from the Australian Synchrotron Research Program.

McDonald, D. and Webb, J.A., 2008. Release of heavy metals from AMD treatment sludges - implications for managing sludge in perpetuity. Proceedings 6th Australian Workshop on Acid Drainage, Burnie, April 2008.

McDonald, D. M., Webb, J. A. and Taylor, J., 2006. Chemical stability of acid rock drainage treatment sludge and implications for sludge management. Environmental Science and Technology, 40(6), 1984-1990.

McDonald, D.M., Webb, J.A. and Musgrave, R.M. 2006. The effect of neutralisation method and reagent on the rate of Cu and Zn release from Acid Rock Drainage treatment sludges. 7th ICARD Conference, March 2006, St Louis, USA.

McDonald, D. and Webb, J.A., 2005. Comparison of the chemical stability of ARD treatment sludges precipitated using conventional lime neutralisation and the High Density Sludge process. Proceedings International Conference on Mining and the Environment, June 27 - July 1, 2005, Skelleftea, Sweden, 705-715.

Neutralisation using limestone, particularly anoxic and open limestone drains

Our studies have looked at natural remediation of AMD in limestone terrains, and Silvana Santomartino's PhD project (2005) investigated ways of minimising the problem of ferrihydrite armouring of the limestone, and made substantial progress in this regard. She developed predictors for the lifetime of the drains, and also determining the role of carbon dioxide exsolution in drain performance. This work has been carried out in collaboration with Charles Cravotta, Water Resources Division of the US Geological Survey, Pennsylvania.

Santomartino, S.L. and Webb, J.A., 2007. Estimating the longevity of limestone drains in treating acid mine drainage containing high concentrations of iron. Applied Geochemistry, 22, 2344-2361.

Santomartino S. and Webb, J. 2003. An experimental study of the chemistry of iron precipitation within Anoxic Limestone Drains. 6th ICARD Conference, July 2003, Cairns, 1117-1121.

Webb, J.A., 1998. The chemistry of anoxic limestone drain treatment of acid mine drainage. In Weaver, T.R. and Lawrence, C.R. (eds), Groundwater: sustainable solutions, Proceedings International Groundwater Conference, Melbourne, February 1998, 581-585.

Sasowsky, I.D., White, W.B., and Webb, J.A., 1995. Acid mine drainage in karst terranes: geochemical considerations and field observations. In Beck, B.F. and Pearson, F.M. (eds), Karst Geohazards: Proceedings of fifth multidisciplinary conference on sinkholes and the engineering and environmental impacts of karst, April 1995, Tennessee, 241-247. A.A. Balkema, Rotterdam.

Webb, J.A. and Sasowsky, I.D. 1994. The interaction of acid mine drainage with a carbonate terrane: evidence from the Obey River, north-central Tennessee. Journal of Hydrology, 161, 327-346.