Abstract: Previous mining history in Norway has resulted in ongoing release of acid mine drainage. Preservation of the historical sites in mining areas does not allow for remediation technologies that result in significant alteration of the historical landscape. Therefore, alternative remediation techniques such as passive mine water treatment have been tested. The climate in Norway varies from mild coastal climates to artic climates, and one of the challenges with passive treatment systems is the cold winter conditions. Anaerobic treatment systems have been built at Kongens Mine near Røros, at Folldal mines, and at Titania's tailings impoundment near Storgangen Mine. These systems utilize sulfate-reducing bacteria that result in the precipitation of metal sulfides. A full- and pilot-scale system at Kongens Mine and Folldal were built in 2006 to remove copper and zinc from typical ARD in an alpine climate. Previous testing with pilot scale systems at Kongens Mine showed that up to 85% copper and 48% zinc could be removed. At Titania A/S the anaerobic system is designed to remove nickel from neutral waters. At this system over 90% nickel is removed when water flow is regulated at a constant flow. Testing shows that the system can function in cold winter conditions, however, optimal metal removal is achieved under warmer temperatures. Temperatures changes by global climatic warming will not adversely affect these anaerobic systems. However, extreme precipitation events and the resulting rapid fluctuations of ARD runoff will provide a challenge for the effectiveness of these systems.

Abstract: Manganese is a common contaminant of mine water and other waste waters. Due to its high solubility over a wide pH range, it is notoriously difficult to remove from contaminated waters. Previous systems that effectively remove Mn from mine waters have involved oxidising the soluble Mn(II) species at an elevated pH using substrates such as limestone and dolomites. However it is currently unclear what effect the substrate type has upon abiotic Mn removal compared to biotic removal by in situ micro-organisms (biofilms). In order to investigate the relationship between substrate type, Mn precipitation and the biofilm community, net-alkaline Mn-contaminated mine water was treated in reactors containing one of the pure materials: dolomite, limestone, magnesite and quartzite. Mine water chemistry and Mn removal rates were monitored over a 3-month period in continuous-flow reactors. For all substrates except quartzite, Mn was removed from the mine water during this period, and Mn minerals precipitated in all cases. In addition, the plastic from which the reactor was made played a role in Mn removal. Manganese oxyhydroxides were formed in all the reactors; however, Mn carbonates (specifically kutnahorite) were only identified in the reactors containing quartzite and on the reactor plastic. Magnesium-rich calcites were identified in the dolomite and magnesite reactors, suggesting that the Mg from the substrate minerals may have inhibited Mn carbonate formation. Biofilm community development and composition on all the substrates was also monitored over the 3-month period using denaturing gradient gel electrophoresis (DGGE). The DGGE profiles in all reactors showed no change with time and no difference between substrate types, suggesting that any microbiological effects are independent of mineral substrate. The identification of Mn carbonates in these systems has important implications for the design of Mn treatment systems in that the provision of a carbonate-rich substrate may not be necessary for successful Mn precipitation. (c) 2006 Elsevier Ltd. All rights reserved.