The Remediation of Tetrachloroethylene by Surfactant Flushing in Both the Saturated and the Unsaturated Zone

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.