Assessing the potential for beneficial reuse of passively-treated mine waters for livestock watering and crop irrigation

Abstract

Passive treatment of mine drainage provides demonstrated water quality improvements and substantial removal of ecotoxic metals via biogeochemical, microbiological, and physical mechanisms. When mine drainage is treated to a quality that satisfies the pertinent ambient water quality criteria, it is often discharged into a receiving water body. If sufficiently treated mine water could be safely reused in agricultural applications – crop irrigation or livestock watering –available surface and groundwater reserves could be freed up for other beneficial uses. Three common Oklahoma crops – field corn (Zea mays var. indentata), sorghum (Sorghum bicolor), and Bermuda grass (Cynodon dactylon) – were irrigated in potting mix from seed with either groundwater from Canadian River alluvium or treated lead-zinc mine water from the effluent of the Mayer Ranch Passive Treatment System (Tar Creek Superfund Site, Commerce, OK). Crop growth and chemical composition were monitored through regular measurements of above-ground height and growth stage as well as final determinations of biomass production and trace metals concentrations. Mine water irrigation did not have a significant effect on seedling emergence, plant growth, or biomass production for corn or Bermuda grass, whereas sorghum exhibited a temporary reduction in growth and a decrease in biomass production under mine water irrigation. The crops were exposed to metals in irrigation waters, fertilizer, and commercial potting mix; irrigation was the smallest contributor of many of the metal species. Cd, Na, and S accumulated in mine water-irrigated substrate. Mine water irrigation did not significantly increase concentrations of Fe, Mn, Zn, K, Ni, or Pb in any of the three species, had mixed effects on Ca concentrations, and increased concentrations of Cd in roots and Mg in belowground and aboveground biomass of some structures. Na and S concentrations in some corn and sorghum root structures and in all Bermuda grass biomass were elevated by mine water irrigation. Hard-rock, net-alkaline mine drainage can be treated in ecologically-engineered systems and reused for the irrigation of some plant species without detriment to emergence patterns, growth, or biomass production. Conversely, passively-treated mine water reuse for livestock watering would be limited by high sulfate levels and transportation costs.