Sulfate removal from mine leachate - development of full-scale bioreactor system (SULFREM)

Important results from the project

The project has achieved its objective to remove more than 90% of sulfate in laboratory experiments, to design and build a full-scale sulfate removal plant, to avoid emissions of hydrogen sulfide from the plant, and to investigate the feasibility for recovering metals that may accumulate in the bioreactor. The bioreactor´s performance has been limited by the availability of lactic acid, but this will be addressed in future experiments by, among other things, the addition of other carbon sources.

Expected long term effects

Sulfate discharges from mining are increasingly included in the environmental permitting process in Sweden, and a number of mines currently need to consider discharge requirements that include sulfate. The long-term goal is for the SULFREM technology to be scaled up and implemented at several mining facilities to contribute to reduced sulfate levels in outgoing water. In the long term, implementation of the technology should facilitate the permitting process.

Approach and implementation

The SULFREM technology in the project was developed through laboratory and field trials. The laboratory experiments established that a high sulfate removal rate could be achieved, which was then scaled up for implementation in a full-scale plant. In the plant, sulfate removal was confirmed, but the removal rate was limited by the availability of lactic acid (carbon source used in the process). The collaboration between all partners has worked very well and has led to further research projects.