Comparative analysis of SEAR, ISCO, and S-ISCO for remediation of aged hydrocarbon-contaminated soils

• Column studies simulated field conditions for SEAR, ISCO, and S-ISCO. • S-ISCO achieved up to 44.2 % TPH removal in column experiments. • SDS minimized non-productive oxidant use, enhancing S-ISCO in columns. • S-ISCO avoided the need for post-treatment of extracted effluents in columns. This study evaluates the effectiveness of Surfactant-Enhanced Aquifer Remediation (SEAR), In Situ Chemical Oxidation (ISCO), and Surfactant-Enhanced In Situ Chemical Oxidation (S-ISCO) for remediating aged fuel-contaminated soil. Experiments were conducted using real sandy loam soil contaminated with 5556 mg/kg of Total Petroleum Hydrocarbons (TPHs). The study employed two surfactants: anionic sodium dodecyl sulfate (SDS) and nonionic E-Mulse® 3 (E3), both at 5 g/L, and sodium persulfate (PS) 40 g/L activated with 13.5 g/L NaOH as the oxidant. Column experiments were performed, simulating field conditions by injecting six pore volumes (PV 26-29 mL each) of treatment solutions over 480 h. SEAR tests achieved TPH removals of 12.3 % with SDS and 14.8 % with E3, highlighting effective desorption but necessitating more PVs or higher surfactant concentration and on-site treatment of extracted solutions. ISCO with alkaline PS removed 23 % of TPHs, indicating limited oxidant access to sorbed contaminants. S-ISCO showed superior performance, achieving TPH removals of 44.2 % with SDS and 39.3 % with E3, eliminating the need for contaminated effluent extraction and treatment on site. The use of SDS demonstrated lower non-productive oxidant consumption and slighter oxidation efficiency enhancement. These findings underscore S-ISCO potential for improving TPH degradation, optimizing resource use, and reducing operational complexities in field applications.