Barrier system for the treatment of nitrogen effluents from the Malmberget iron mine

• Main Authors: Herbert, Roger, Björnström, Joakim
• Format: Conference Object
• Language: English
• Published: Uppsala universitet, Luft-, vatten- och landskapslära 2009
• Subjects: Mineral and Mine Engineering; Mineral- och gruvteknik; Earth and Related Environmental Sciences; Geovetenskap och miljövetenskap; Linaälv; Malmberget; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-117758

At the Malmberget iron mine in northern Sweden, nitrogen from undetonated explosives is discharged from the mine with process water. After passing through a settling pond, excess process water is discharged to the Linaälv River via a spillway. Because of the risk for eutrophication in rivers and coastal areas downstream, it is necessary to decrease the N levels in the effluent waters. This study presents the results from laboratory column experiments under water – saturated conditions, conducted at room temperature and 5oC, which will be used in the design of a pilot-scale barrier system. The columns were filled with a reactive substrate consisting of sawdust and activated sewage sludge. The results of the room temperature experiments demonstrated that nitrate removal efficiency was >95% for flow rates < 341 liters d-1 m-3 reactive mixture. However, at flow rates of ~700 liters d-1 m-3 reactive mixture, nitrate removal efficiency decreased to ~64%. Tracer experiments indicated an increasing degree of channeling in the columns as flow rate increased, thus leading to a reduction in removal efficiency. Apparent denitrification rates were estimated to 2.8 -9.3 g N d-1 m-3 and 2.2 g N d-1 m-3 at room temperature and 5oC, respectively.