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Hulshof, A. H. M., Blowes, D. W., & Douglas Gould, W. (2006). Evaluation of in situ layers for treatment of acid mine drainage: A field comparison. Water Res, 40(9), 1816–1826.
Abstract: Reactive treatment layers, containing labile organic carbon, were evaluated to determine their ability to promote sulfate reduction and metal sulfide precipitation within a tailings impoundment, thereby treating tailings effluent prior to discharge. Organic carbon materials, including woodchips and pulp waste, were mixed with the upper meter of tailings in two separate test cells, a third control cell contained only tailings. In the woodchip cell sulfate reduction rates were 500 mg L-1 a-1, (5.2 mmol L-1 a-1) this was coupled with the gradual removal of 350 mg L-1 Zn (5.4 mmol L-1). Decreased δ13CDIC values from -3‰ to as low as -12‰ indicated that sulfate reduction was coupled with organic carbon oxidation. In the pulp waste cell the most dramatic change was observed near the interface between the pulp waste amended tailings and the underlying undisturbed tailings. Sulfate reduction rates were 5000 mg L-1 a-1 (52 mmol L-1 a-1), Fe concentrations decreased by 80–99.5% (148 mmol L-1) and Zn was consistently <5 mg L-1. Rates of sulfate reduction and metal removal decreased as the pore water migrated upward into the shallower tailings. Increased rates of sulfate reduction in the pulp waste cell were consistent with decreased δ13CDIC values, to as low as -22‰, and increased populations of sulfate reducing bacteria. Lower concentrations of the nutrients, phosphorus, organic carbon and nitrogen in the woodchip material contribute to the lower sulfate reduction rates observed in the woodchip cell.
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Jarvis, A. P., & Younger, P. L. (2001). Passive treatment of ferruginous mine waters using high surface area media. Water Res., 35(15), 3643–3648.
Abstract: Rapid oxidation and accretion of iron onto high surface area media has been investigated as a potential passive treatment option for ferruginous, net-alkaline minewaters. Two pilot-scale reactors were installed at a site in County Durham, UK. Each 2.0m high cylinder contained different high surface area plastic trickling filter media. Ferruginous minewater was fed downwards over the media at various flow-rates with the objective of establishing the efficiency of iron removal at different loading rates. Residence time of water within the reactors was between 70 and 360s depending on the flow-rate (1 and 12l/min, respectively). Average influent total iron concentration for the duration of these experiments was 1.43mg/l (range 1.08-1.84mg/l; n=16), whilst effluent iron concentrations averaged 0.41mg/l (range 0.20-1.04mg/l; n=15) for Reactor A and 0.38mg/l (range 0.11-0.93mg/l; n=16) for Reactor B. There is a strong correlation between influent iron load and iron removal rate. Even at the highest loading rates (approximately 31.6g/day) 43% and 49% of the total iron load was removed in Reactors A and B, respectively. At low manganese loading rates (approximately 0.50-0.90g/day) over 50% of the manganese was removed in Reactor B. Iron removal rate (g/m3/d) increases linearly with loading rate (g/day) up to 14g/d and the slope of the line indicates that a mean of 85% of the iron is removed. In conclusion, it appears that the oxidation and accretion of ochre on high surface area media may be a promising alternative passive technology to constructed wetlands at certain sites.
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