A generic methodology for the prediction, prevention and remediation of the AMD phenomenon was developed including the following; identification of AMD sources, sampling and characterisation; drainage monitoring; static and kinetic tests for predicting the AMD potential and quality; chemical modelling of the reactions involved; drainage prediction from spoils versus time. Within the project several preventive technologies were tested, such as the application of alkaline additives and covers. Remedial technologies developed include innovative neutralisation schemes with magnesia in combination with sulphate reducing bacteria, and passive treatment schemes with anoxic limestone drains and anaerobic wetlands. These findings provided the basis for the development of a mine closure strategy. The expertise and methodologies acquired within the project, already transferred to the endorsing Kassandra Mines, can potentially be used by other similar sulphide mines, in order to aid sustainable development in the mining sector in Europe.
Polymetallic sulphide mines, active or redundant, constitute a potential source of pollution because of acid mine drainage (AMD), which is generated by direct or indirect oxidation of sulphidic minerals when exposed to the action of water and oxygen. AMD consists of acidic solutions containing toxic and undesirable elements, as Fe, Cu, Zn, Pb, Cde, As etc. released to the environment. This is widely considered to be the most serious environmental problem caused by mining, particularly because AMD pollution can continue for some decades after mine closure. Potential sources of AMD generation are waste dumps, tailings dams, concentrate stockpiles, and old mining works.
The proposed research is directed at developing a methodology for the effective prediction, prevention, control and mitigation of AMD pollution in polymetallic sulphide mining/milling operations, and an appropriate mine closure strategy.
The major research tasks are:
1. identification of sites with a potential for AMD generation, chemical, mineralogical and bacteriological characterization,
2. development of the appropriate techniques for the prediction of AMD generation capacity,
3. development of a chemical model of the AMD generation process taking into account the thermodynamics and kinetics of the complex oxidation-dissolution and precipitation reactions that are involved,
4. evaluation and development of preventive and remedial technologies to combat AMD,
5. development of the appropriate waste management and solid tailings disposal technique(s),
6. development of a mine closure strategy so as to avoid future AMD generation.
Successful completion of the project will greatly assist in pollution abatement in the polymetallic sulphide mining operations. The development of cost-effective and environmentally safe techniques will contribute to further advancement of the industry. The potential for technology transfer within and outside Europe is very large, involving not only active, but redundant mine sites as well.
Funding SchemeCSC - Cost-sharing contracts
SW7 2BP London