Evaluation of Techniques for Estimating Metal Leachability from Solid Wastes Blended with Granular Materials

Combining solid wastes with granular materials is commonly performed for various recycling applications. Traditional methods for assessing risk from land-applied waste materials involve a batch-leaching test on a waste by itself. This may not be an accurate means of estimating leaching risk from a waste material once blended with native soil or other granular material. Four different methods of estimating leaching risk from scrubber product and wood–tire ash blended with granular materials were assessed. Data indicate that leaching from the waste material alone is an excessively conservative estimate when compared to leaching on the blends themselves. Measured leaching from the blended materials followed a linear relationship with waste blend percentage and may be useful for interpolating concentrations. Mathematically reducing leachate concentrations proportionate to the mass of waste in the blend yielded the least conservative estimates, even when accounting for blend pH. Arsenic leaching from the scrubber product blends was often twice as high as mass-based dilution estimates. Elements such as As, V, Zn, and Pb leached higher in actual blends than would be expected based on 1:1 mass dilutions. This study provides risk assessment insights into the efficacy of different leaching risk estimation methods for blended waste materials.