Geochemistry of a Permeable Reactive Barrier for Metals and Acid Mine Drainage

Abstract

A permeable reactive barrier, designed to remove metals and generate alkalinity by promoting sulfate reduction and metal sulfide precipitation, was installed in August 1995 into an aquifer containing effluent from mine tailings. Passage of groundwater through the barrier results in striking improvement in water quality. Dramatic changes in concentrations of SO 4 (decrease of 2000-3000 mg/L), Fe (decrease of 270-1300 mg/L), trace metals (e.g., Ni decreases 30 mg/L), and alkalinity (increase of 800-2700 mg/L) are observed. Populations of sulfate reducing bacteria are 10 000 times greater, and bacterial activity, as measured by dehydrogenase activity, is 10 times higher within the barrier compared to the up-gradient aquifer. Dissolved sulfide concentrations increase by 0.2-120 mg/ L, and the isotope 34 S is enriched relative to 32 S in the dissolved phase SO 4 2within the barrier. Water chemistry, coupled with geochemical speciation modeling, indicates the pore water in the barrier becomes supersaturated with respect to amorphous Fe sulfide. Solid phase analysis of the reactive mixture indicates the accumulation of Fe monosulfide precipitates. Shifts in the saturation states of carbonate, sulfate, and sulfide minerals and most of the observed changes in water chemistry in the barrier and downgradient aquifer can be attributed, either directly or indirectly, to bacterially mediated sulfate reduction.

Treatment of Acidic Groundwater in Acid Sulfate Soil Terrain Using Recycled Concrete: Column Experiments

“…Alternatively, soil liming to neutralise the soil and groundwater acidity has also been practiced. Such an approach can be effective but often involves high operating costs and produces metal-rich sludge in the soil (Benner et al 1999), from which metals may subsequently leach when mixed with freshly produced acid in the groundwater. These conventional strategies target acidity production along the hydro-geological pathway from the soil profile to the discharge point, but do not address the acidity already present in the soil and groundwater.…”

Acid Water Neutralization Using Microbial Fuel Cells: An Alternative for Acid Mine Drainage Treatment

“…Therefore, AMD treatment has been one of the major focus of study in recent decades [2][3][4][5]. Unfortunately, conventional treatment technologies for AMD remediation have several limitations, both economic and operational [6].…”

Kinetic of biogenic sulfide production for microbial consortia isolated from soils with different bioaccessible concentrations of lead

“…These electron donors can either be completely oxidized to CO 2 or partially oxidized to acetic acid, depending on the SRB strain. In the presence of a lactate ion, the simplified reaction of the complete mineralizing process is (Benner et al 1999)…”