Alternative waste residue materials for passive in situ prevention of sulfide-mine tailings oxidation: a field evaluation.
Novel solutions for sulfide-mine tailings remediation were evaluated in field-scale experiments on a former tailings repository in northern Sweden. Uncovered sulfide-tailings were compared to sewage-sludge biosolid amended tailings over 2 years. An application of a 0.2m single-layer sewage-sludge amendment was unsuccessful at preventing oxygen ingress to underlying tailings. It merely slowed the sulfide-oxidation rate by 20%. In addition, sludge-derived metals (Cu, Ni, Fe, and Zn) migrated and precipitated at the tailings-to-sludge interface. By using an additional 0.6m thick fly-ash sealing layer underlying the sewage sludge layer, a solution to mitigate oxygen transport to the underlying tailings and minimize sulfide-oxidation was found. The fly-ash acted as a hardened physical barrier that prevented oxygen diffusion and provided a trap for sludge-borne metals. Nevertheless, the biosolid application hampered the application, despite the advances in the effectiveness of the fly-ash layer, as sludge-borne nitrate leached through the cover system into the underlying tailings, oxidizing pyrite. This created a 0.3m deep oxidized zone in 6-years. This study highlights that using sewage sludge in unconventional cover systems is not always a practical solution for the remediation of sulfide-bearing mine tailings to mitigate against sulfide weathering and acid rock drainage formation.
Division of Geosciences and Waste Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden. Electronic address: peter.nason@ltu.se.
Peter
P
Nason
Crustal Geophysics and Geochemistry Science Center, U.S. Geological Survey, Denver Federal Center, P.O. Box 25046, MS 964D, Denver, CO 80225-0046, USA.
Raymond H
RH
Johnson
Niras, Box 70375, SE-107 24 Stockholm, Sweden.
Clara
C
Neuschütz
Division of Geosciences and Waste Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.
Lena
L
Alakangas
Division of Geosciences and Waste Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.
Björn
B
Öhlander
D060729:Coal Ash / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D008670:Metals / Q000032:analysis / Q000737:chemistry; D008906:Mining; D010084:Oxidation-Reduction; D012722:Sewage / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis; D013440:Sulfides / Q000737:chemistry*; D013548:Sweden; D014874:Water Pollutants, Chemical / Q000032:analysis
D060729:Coal Ash; D007220:Industrial Waste; D008670:Metals; D012722:Sewage; D012989:Soil Pollutants; D013440:Sulfides; D014874:Water Pollutants, Chemical
Acid rock drainage; Biosolid; Fly ash; Sewage sludge