Metals in Waste Foundry Sands and an Evaluation of Their Leaching and Transport to Groundwater

While most waste foundry sands (WFSs) are not hazardous, regulatory agencies are often reluctant to permit their beneficial use in agricultural and geotechnical applications due to concerns over metal leaching. The objective of this study was to quantify total and Toxicity Characteristic Leaching Procedure (TCLP) metals in 16 waste sands from Brazilian ferrous foundries then assess their potential to leach to ground-water using a probabilistic model. Total and TCLP metal concentrations in the non-hazardous sands fell within ranges as reported in the literature, although some of the leachate concentrations were found to exceed drinking water and groundwater maximum contaminant levels (MCLs). Leachate values above the MCLs were then used in the model to estimate groundwater concentrations at hypothetical wells up to 400m downgradient from a land application unit. A conservative scenario of 1 ha of land applied WFS, and high annual rainfall totals (low evaporation) suggested that groundwater concentrations of Ba, Hg, Mn, Ni, and Pb could potentially exceed health-based MCLs at most wells. While a wet climate can exacerbate the transport of metals, land application of WFSs in areas with moderate rainfall totals or high rainfall, high evaporation was predicted to be protective of groundwater quality and human health.