A Numerical Model to Study Pulsing Soil Flushing: Validation and Application to a Real Contaminated Soil

A numerical model for simulating soil flushing by chelating agents, for the remediation of heavy metals contaminated soils, is presented. The solubilization and transport of Pb was simulated during the percolation of EDTA, applied in a pulse mode. Results were validated through column tests on a real Pb contaminated soil. The model accounts for transport of EDTA (EthyleneDiamine Tetraacetic Acid), EDTA-Pb chelates and the Pb solubilization process. A finite difference technique (FDT) with a multistep approach was applied to prevent numerical diffusion effects on the solution. The model also takes into account the reduction in soil permeability by soil dissolution. Results from the simulation include eluted Pb and residual chelate concentrations and residual Pb into the soil. Once validated the model was used to simulate a multi-pulse treatment, in order to verify the proper chelate dosage and number of pulsing steps. The model thus represents an effective tool for flushing unit design and planning of in situ or ex situ remediation activities.