Environmental impacts of mining can be minimised by removing nitrogen compounds of non-detonated explosives with bioreactor treatment. Bacteria in the mine water together with new design solutions intensified the cleaning process so that removal of 90 % total nitrogen can be reached at +5°C. Preliminary research results showed that low temperature has not significantly reduced the biological nitrogen removal in the bioreactor.
Biological removal of nutrients from mine water has been studied for one year in the KAIRA-project at the Finnish Forest Institute Rovaniemi Unit together with the Geological Survey of Finland and industrial partners. Major funding organizations are Tekes Finnish Funding Agency for Technology and Innovations and the European Regional Development Fund.
Major challenges in study are the low temperature of mine water and due to large water volumes the low concentration of total nitrogen. The water-soluble ammonium and nitrate are originally from non-detonated explosive. Removal of those will require aerobic and anaerobic treatment before nitrogen will be released to the atmosphere. The amount of mine water formed per year is up to millions of cubic meters depending on mine. The mine water will differ from landfill waters on its low biological oxygen demand and content of nutrients. Now the mine water is treated in ponds.
The next aim of project is to reach an economical bioreactor process. A large-scale bioreactor will be build to Outokumpu Tornio Works´n Kemin mine to obtain results for full scale operation. The new bioreactor should operate at a hydraulic retention time below the current one hour. Also the natural nitrogen removal and possibilities to intensify it in mines are included in the study.
Project members: Outokumpu Tornio Works Kemin mine, Scan Mining Oy Pahtavaara mine, Kemphos Oy Siilinjärvi mine, Agnico-Eagle Finland Kittilä Mine, Scandinavian Minerals Ltd. (Kevitsa), Anglo American Explorations B.V. plc, Oy Forcit Ab, Tekno-Forest Oy, Sarlin Hydor Oy and Geological Survey of Finland, Mineral Processing.