Abstract
Column and box experiments were performed to evaluate the efficiency of surfactant flushing for remediation of non-aqueous phase liquid (NAPL) in water saturated and unsaturated sands under controlled conditions. Tetrachloroethylene (PCE) was selected as the NAPL and a 1 % solution of sorbitan monooleate as the surfactant to be studied. Four column experiments using Ottawa sand and sand from the aquifer at Canadian Forces Base Borden were performed by flushing a 1 % sorbitan monooleate solution through the columns under saturated and unsaturated conditions, and their results were compared to the results of column experiments that flushed water only. Two-dimensional box experiments with Ottawa sand were duplicated in the unsaturated condition. Both in the saturated and the unsaturated column experiments, less than 0.5 % of the original mass of PCE remained in the column after flushing 12 pore volumes of a 1 % sorbitan monooleate solution. Mass removed from the saturated column as dissolved phase accounted for more than 98 % of PCE removed and more than 91 % of PCE was removed from the unsaturated column. Approximately 9 % of the mass of PCE was estimated to have been lost by volatilization during the unsaturated column experiments. In the unsaturated box experiment, 85 % of the initial PCE was removed from the effluent within 5 pore volumes of surfactant flushing and 0.5 % of the initial mass of PCE remained in the box.
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