Reduction of nitrogen discharges in mining processes and mitigating its environmental impact miNing
|Coordinator||Sveriges Lantbruksuniversitet - Institutionen för vatten och miljö|
|Funding from Vinnova||SEK 5 526 000|
|Project duration||July 2014 - December 2018|
|Venture||The strategic innovation programme for Swedish mining and metal producing industry - SIP Swedish Mining Innovation|
Purpose and goal
All aims of miNing have been achieved, i.e. 1) to plan, construct and operate a bioreactor for removal of nitrate from mine leachate and runoff, 2) to study the dynamics of water percolation and nitrate production in two small-scale waste rock dumps during two hydrological years in Kiruna, 3) to provide a better understanding of the possibilities to use denitrification occurring in anaerobic tailings pond sediments as a passive nitrogen removal method, and 4) to increase knowledge on the N removal potential of especially different plant species in subarctic wetlands.
Expected results and effects
As a result of miNing, a full-scale bioreactor system was constructed in Kiruna in 2018 for the treatment of leachate discharging from a waste rock dump. Monitoring of the waste rock dumps indicated that leachate production from the small dumps only occurred during snowmelt and on occasions with high precipitation intensity. The nitrogen reduction rate found in this mesocosm study over an 85-day summer period was in the range 0.050.1 mg NO3-N/L/day. The N removal potential of wetlands varied among plants species and lifeforms and the most efficient combinations were identified.
Planned approach and implementation
miNing has had a structure and implementation where different methods for removing nitrogen from drainage water have been investigated at different scales. The 3-year program period (later extended to 4 years) has offered sufficient time for monitoring and follow-up studies. The project has been conducted as three PhD student projects, which was required for a sufficiently long timeframe for adequate sampling and data analysis. Process understanding has benefited from the use of PhD students in the project where the different systems could be studied over a period of several years.