SOIL CLEANUP BY SURFACTANT WASHING .3. DESIGN AND EVALUATION OF THE INTEGRATED PILOT-SCALE SURFACTANT RECYCLE SYSTEM

A pilot-scale system for recycle and reuse of spent surfactant solution from organic-contaminated soil washing was successfully tested. The surfactant recycle system is comprised of an air-stripping column to remove volatile contaminants, a solvent-extraction column to remove nonvolatile contaminants, and a solvent-recovery system to remove and concentrate nonvolatile contaminants from the solvent. The pilot-scale recycle system was operated in conjunction with a soil test bed which was spiked with biphenyl as a representative ''nonvolatile'' contaminant. The individual components, which had each been tested previously, were operated together as an integrated system to produce a recycled surfactant solution which was reused during the test. The operation of this system is discussed and the results from the integrated testing are presented. Not only was 99% biphenyl removal from soil achieved in 7.7 pore volumes of 2.5 wt% sodium dodecyl sulfate surfactant solution, but there was also no decrease in the effectiveness of the recycled surfactant solution in removing the biphenyl compared to the virgin solution. Approximately 1 mg/kg biphenyl remained in the soil after surfactant washing.