Authors: R. Philippe, D. Nel, T. Clarke
Enviromine2009, Santiago Chile, October 2nd, 2009
Abstract
Discharge criteria for mining effluents have undergone a radical review worldwide over the
past number of years. As a result, conventional treatment technologies such as lime
neutralisation are often no longer an acceptable or viable standalone treatment regime. A key
limitation of treatment with lime is the maximum sulphate reduction that can be achieved based
on the saturation level of gypsum (calcium sulphate) in water. Several countries have now
adopted a discharge standard that reduces the permissible levels of sulphates in mine effluents.
To meet these new demanding standards, more advanced treatment technologies are being
developed and deployed.
This paper reviews some of the available technologies for sulphate removal from mining
effluents, including current developments in the Southern Hemisphere, especially Australia,
South Africa and South America. The objective will be to provide a technology selection
overview that can be used as a guideline to make preliminary feasibility estimates, as part of a
more comprehensive effluent mitigation strategy and planning process.
Technologies that will be reviewed include membrane based systems, (biological) sulphate
reduction methods and sulphate precipitation techniques. It is a common misunderstanding to
consider membranes or ion exchange as sulphate removal technologies from effluents. Both
technologies merely concentrate sulphates in (liquid) reject streams, they do not remove
sulphate from the water inventory. All current technologies use either precipitation or
conversion processes for the sulphate removal, eventually combined with a concentration
process such as reverse osmosis, nanofiltration or ion exchange.
