Effects of hydraulic circulation induced by gravel lenses of varying sizes on nitrobenzene removal in heterogeneous aquifers during air sparging remediation

Abstract

Air sparging (AS) technology is widely used in groundwater remediation of organic contaminants. In this study, using a two-dimensional physical model, the research explores how varying sizes of gravel lenses affect airflow distribution, hydraulic circulation, and contaminant removal efficiency. The presence of gravel lenses was found to significantly enhance hydraulic circulation, thereby improving the removal of nitrobenzene. The study revealed that the length and height of the gravel lenses play crucial roles in determining the airflow pattern and the extent of hydraulic circulation. A lens length of 5 cm was sufficient to form a hydraulic circulation zone, while a lens height of 4 cm was necessary for effective bubble migration. As the lens thickness increased, the bubble migration path extended, enhancing the bubble pulsation effect and the remediation zone. However, beyond the thickness of 10 cm, further increases in lens thickness did not significantly improve removal efficiency, likely due to stable gas-liquid mass transfer rates. The study concluded that gravel lenses were essential for establishing hydraulic circulation in AS processes, which could lead to more effective remediation strategies in heterogeneous aquifers. These findings provide valuable insights for optimizing AS system designs in complex geological settings.