Centrifuge modeling of in situ surfactant enhanced flushing of diesel contaminated soil

In this research the effectiveness of physical modeling of in situ flushing with water and a surfactant solution was evaluated using a geotechnical centrifuge. The centrifugal experiments consist of two parts: transport of diesel through fine grain soils and remediation of diesel contaminated soil. First, 7.74 m³ of diesel per meter (width) was infiltrated into a 15 m thick prototype layer of fine grain unsaturated soil. Then contaminated soil was remediated by continuous flushing with two liquids (water and 1% (wt/v) aqueous solution of sodium dodecyl sulfate (SDS) surfactant) while subjecting the sample to 50 g acceleration. Effectiveness of soil remediation by flushing with 1% (wt/v) SDS surfactant was investigated in this research and compared that to flushing with water without additives. The total volume of injected remediation solution over 130 prototype days was equal to 4.20 times the pore volume of the soil between two barrier walls. The results showed that when surfactant solution was used, the elutriate flow was downward congruent with the remediation goal. On the other hand, when water without surfactant was used, the contamination plume expanded in the lateral direction which exacerbated the situation. The test results also showed a considerable reduction (76.3%) of diesel content in soil after flushing with SDS solution after 130 days of flushing. Based on the test results it was concluded that the geotechnical centrifuge and the described experimental procedure could be used as a design tool for implementation and evaluating the effectiveness of in situ surfactant-enhanced flushing remediation systems.