The effectiveness of surfactants for remediation of organic pollutants in the unsaturated zone

In laboratory experiments performed to evaluate the efficiency of surfactant flushing for remediation of non-aqueous phase liquid (NAPL) in the unsaturated zone, less than 0.001% of the original mass of tetrachloroethylene (PCE) remained in the column after 15 pore volumes of a 1% sorbitan monooleate solution or after 7 pore volumes of a 1% Ethomid O/17 solution were passed through the columns. Mass removed as dissolved phase in the effluent accounted for more than 90% of PCE removed the remainder was lost by volatilization. To determine the influence of parameters that may affect the remediation process, column tests were repeated with different values of parameters, including grain size, application rate, surfactant type, surfactant concentration, and solution viscosity. The results from the column experiments were simulated with the two-dimensional finite element computer code for multiphase flow and transport, MOTRANS. Results of the simulation were similar to those from the experiments. Both experimental and modeling results suggest that surfactant flushing has a great potential to remove mass from NAPL in the unsaturated zone.