Evaluation of the Impact of Environmental Conditions on Constituent Leaching from Granular Materials During Intermittent Infiltration

Abstract

Rapid testing procedures are desirable for evaluating leaching from secondary materials being considered for beneficial use in construction or disposal. Often, column leaching tests are considered a surrogate for field data, providing a basis to estimate constituent release under field conditions of intermittent infiltration. This dissertation evaluates the use of batch leaching tests providing information as a function of pH and liquid to solid ratio as a basis for estimating constituent leaching under intermittent percolation. Batch testing results are compared to column testing under unsaturated, intermittent flow and continuous saturated flow. Extrapolations from batch testing based on empirical relationships of pH and liquid to solid ratio and the use of geochemical speciation modeling to represent leaching behavior are examined. Uncertainties as a consequence of each extrapolation basis are quantified. Five granular materials with potential for reuse were evaluated: municipal solid waste incinerator bottom ash, coal fly ash, aluminum recycling residue, construction demolition debris, and a synthetic cement mortar. Two of these materials were tested under two different aging conditions. Results showed no significant difference between the continuously saturated and intermittent unsaturated column flow regimes, agreement in most cases between batch and column testing, including cumulative release, and a decrease in constituent release due to carbonation. Geochemical speciation modeling results for three selected materials agree with experimental batch data and may be used for long-term constituent release prediction.