EVALUATION OF AN ULTRAFILTRATION METHOD FOR SURFACTANT RECOVERY AND REUSE DURING IN-SITU WASHING OF CONTAMINATED SITES - LABORATORY AND FIELD STUDIES

Feasibility studies were conducted on the use of ultrafiltration to recover surfactant from aqueous waste streams generated from the in situ surfactant washing of a site contaminated with polychlorinated biphenyls (PCBs) and oils. A Romicon Model HF-Lab-5 ultrafiltration unit and three types of ultrafiltration membranes (PM500, XM50, and CM50) were evaluated for their permeability to a nonionic surfactant previously selected for the in situ washing. Results from laboratory studies using the XM50 membrane cartridge showed that 78 percent of the surfactant passed through the membrane surface (permeate) and was recovered. Two field-pilot tests of the ultrafiltration system were conducted using leachate containing a mixture of water, oils, PCBs, and surfactant that was collected from an in situ surfactant-washing demonstration test. Forty-six percent of the surfactant (mass) was recovered during the first field test using the XM50 membrane. The membrane retained 94 percent of the PCBs and 89 percent of the oils. The second field test showed that the PM500 membrane recovered 67 percent of the surfactant in the permeate and retained more than 90 percent and 83 percent of the PCBs and oils, respectively. This study indicates that a significant volume of a nonionic surfactant can be recovered from leachate mixture containing PCBs and oils by ultrafiltration. The recovered surfactant could be reused to improve the economic viability of in situ surfactant washing of contaminated sites.