HR: 1340h
AN: H13G-1677    [Abstracts]
TI: Evaluation of Reactive Mixtures for Treatment of Mine Drainage From a Waste Rock Storage Area in Northern Saskatchewan, Canada
AU: * Jeen, S
EM: sjeen@uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada
AU: Bain, J G
EM: jbain@uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada
AU: Blowes, D W
EM: blowes@uwaterloo.ca
AF: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada
AB: A column experiment has been conducted to evaluate the performance of three reactive mixtures which may be used in a permeable reactive barrier (PRB) for the treatment of low quality mine drainage water from a waste rock storage area in northern Saskatchewan, Canada. The key element of concern in the drainage water is dissolved Ni, which occurs at approximately 13 mg/L. The water is low pH ~4.3, oxidized, contains high concentrations of dissolved sulfate (4400-4750 mg/L), Al (45 mg/L), Zn (3 mg/L), Co (3 mg/L) and relatively low concentrations of other dissolved heavy metals and iron. Three columns, each containing one of the mixtures, were constructed: column A (peat/lime/limestone/gravel), column B (peat/zero valent iron (ZVI) filings (20%/vol)/limestone/gravel), and column C (peat/ZVI filings (10%/vol)/limestone/gravel). The experimental results have shown that the mixtures promote bacterially-mediated sulfate reduction and metal removal by precipitation of metal sulfides, metal precipitation, and adsorption under relatively high pH conditions (pH of 7 to 8). Reducing conditions (Eh of 0 to -200 mV) have developed in all of the columns, from the highly oxidized influent water (Eh of +500 to +600 mV). Hydrogen sulfide is detected in the effluent water, and dissolved sulfate concentrations decrease by several hundred mg/L. Based on sulfate removal, sulfate reduction occurs more strongly in columns B and C than column A. All of the columns are removing Ni to below the limit of detection (typically < 0.01 mg/L); however, the removal rate in column A is slower than in columns B and C and has decreased over time. Most other metals are removed to low concentrations in all of the columns. The results suggest that while the longevity of mixtures including ZVI will be much longer than mixtures containing only peat, considering economic aspects, the PRB consisting of only peat could also be an alternative option, if breakthrough time can be predicted and replacement of peat can be conducted in a timely manner. This study shows that the use of reactive mixtures that facilitate microbial activities and redox reactions in subsurface could be a valuable means to remove various metal contaminants originated from mine drainage sites.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting