Injection of alkaline by products for remediation of weathered mine waste

Purpose and goal

The aim with the study was to gain more knowledge about a new method for remediation/reclamation of weathered waste rock deposits and old mining waste areas. Questions to be answered were if green liquor dreg from various pulp and paper facilities could be used (or if it would be ´facility-specific´) and if the method could be applied in an actual mine waste deposit, which had not been built for the purpose. The study was able to answer these questions and fill in the knowledge gaps that were essential for a coming full-scale trial.

Results and expected effects

Smaller studies were focused on how different green liquor dregs affected water percolation, buffering of pH and decreased metal concentrations in leachates. The results were expected to be positive which was also confirmed by the study. Results from the larger test in an actual deposit was more unpredictable nevertheless with very good results. The green liquor dreg slurry showed a good spreading and was attached to the mine waste. It was expected that the outcome of the study would make a full-scale injection possible within 1-2 years, which now is possible.

Approach and implementation

All parts of the project were well performed and the time schedule could be kept without any problems. The study was started with collecting of the materials (green liquor dregs) and thereafter start of the smaller lab-scale trials. During late summer was the start of the larger test with drilling, pumping, excavation and method evaluation for an actual mine waste deposit. The larger test connected earlier results with new ones and gave a good indication on the overall performance and applicability for the method.