Decoding chlorinated organic compounds removal mechanisms in full-scale electrokinetic remediation systems

• Full-scale EKR reduced COC levels by 44.1% in Sardas landfill sludge in 120h. • Thermal volatilisation identified as the main COC removal pathway. • N 2 -stripping confirmed temperature-driven COC volatilisation from 25 to 75 °C. • Less than 1% of COCs recovered in condensate and filter systems. • Electric field distribution is affected by heterogeneous sludge contamination. • COC desorption enhanced by warm gas streams due to high volatility. This study presents a full-scale enhanced electrokinetic remediation (EKR) experiment aimed at recovering chlorinated organic compounds (COCs) and elucidating their removal mechanisms in contaminated sludge. The experiment was conducted at the lixiviate pond of the Sardas landfill within a 2 × 2 m 2 plot, where COC concentrations initially ranged from 0.3 to 276.0 mmol kg -1 (90 mg kg -1 to 83000 mg kg -1 ). The hypothesis driving this work is that thermal-induced volatilisation is the dominant removal pathway at the field scale. The findings underscore the volatile nature of COCs and the need for targeted recovery strategies. Despite achieving the targeted reduction in COC concentration after 120 hours (>44%) via volatilisation, recovery in flushing fluids, condensate, and filters was minimal (<1%), indicating that, despite having the specialised gas-collector design, the capture was not successful, potentially due to the composition of the volatilised gases. Complementary lab-scale N₂-stripping experiments conducted at temperatures ranging from 25 °C to 75 °C simulated sludge heating and revealed that volatilisation significantly increases with temperature, but also diminishes COC capturing in common adsorbents and absorbents, confirming the thermal sensitivity of COC removal, and helping to understand the results obtained in the larger-scale test. Overall, this work advances understanding of large-scale EKR processes and highlights the advantages and challenges for efficient site decontamination.