Adaptation of selected models for describing competitive per- and polyfluoroalkyl substances breakthrough curves in groundwater treated by granular activated carbon

Granular activated carbon (GAC) has proven to be a successful technology for per- and polyfluoroalkyl substances (PFAS) removal from contaminated drinking water supplies. Proper design of GAC treatment relies upon characterization of media service-life, which can change significantly depending on the PFAS contamination, treatment media, and water quality, and is often determined by fitting descriptive models to breakthrough curves. However, while common descriptive breakthrough models are favored for their ease-of-use, they have a significant shortcoming in that they are not able to properly fit PFAS desorption in competitive sorption scenarios. The present work adapts three common descriptive models to fit competitive PFAS breakthrough curves from a GAC pilot study. The adapted and original models were fit to the experimental breakthrough curves for 12 common PFAS and evaluated using adjusted R² and reduced χ² values. This study found that the novel adaptation of the common descriptive models successfully accounted for desorption of PFAS compounds from the GAC, accurately describing increased exposure risks due to elevated effluent levels during desorption without significantly increasing the complexity of implementing the models.