BIOMET: Efficient metal recovery from mine drainage water by biological treatment

Purpose and goal
The aim of the project was to increase resource efficiency and reduce the environmental footprint of mining by reduced metal emissions through designing smart bioprocesses. The project has reached that goal by suggesting a bioprocess toolbox for mine drainage. Each of the tools in the box has been evaluated with respect to selective metal recovery, investment, energy input, labor, chemical requirement and metal leakage. The tools can have an impact on resource efficiency. However, the environmental benefits will be dominating.

Structure and implementation
Literature reviews were done on i) environmental goals and legislations on national and European level affecting the Swedish mining industry and mine drainage treatment method, ii) selections of mine drainage water from different locations, different mine operation processes and with different quality, and iii) biological treatment methods with respect to efficiency, productivity, cost and variables affecting those. In addition, experiments were performed to bridge literature gaps. The project generated a report, a toolbox, two case studies and a presentation at a conference.

Results
Bioprocesses are potentially competitive in treating drainage in Swedish conditions by high efficiency and decreased sludge cost. However, innovations are required to increase productivity and allow cost-efficient heating. Generally less chemical input is required but the microorganisms need an energy source that affects the performance. The location of the process is also essential. Clearing lakes can be excellent incubators for algae metal sorption but adding fertiliser to compensate low phosphate levels proposes a risk. A toolbox was assessed to address different needs.