SOIL CLEANUP BY SURFACTANT WASHING .2. DESIGN AND EVALUATION OF THE COMPONENTS OF THE PILOT-SCALE SURFACTANT RECYCLE SYSTEM

The components of a pilot-scale system to recycle and reuse a surfactant solution containing contaminants from remediated soil were designed, fabricated and successfully tested. Use of surfactants in soil washing or flushing can expedite remediation manyfold as the aqueous solubility of hydrophobic compounds is increased. The process is of even greater utility when the contaminants are also nonvolatile and nonbiodegradable. Biphenyl was used to represent nonvolatile contaminants. Not only was 99% biphenyl removal (initial concentration 1000 mg/kg) from soil achieved in 7 pore volumes of 2.5 wt% sodium dodecyl sulfate (SDS) solution, but there was no decrease in the effectiveness of the recycled solution in removing the biphenyl compared to the virgin solution. Approximately 1 ppm biphenyl remained in the SDS solution after recycle. Toluene was used to represent volatile contaminants. Toluene removal from the soil test bed was 98% when using the same SDS solution. There was approximately 3 ppm toluene in the recycled surfactant solution. Again, the effectiveness of recycled surfactant solution in removing toluene from soil was the same as the virgin material.