In this study, four commercially available membranes (NF270, NF90, CR100, and SW30) spanning the loose NF to tight RO separation ranges were investigated for their PFAS rejection performance. The specific focus was devoted to evaluating the removal of perfluoroalkyl acids (PFAAs) in a full-scale closed-circuit desalination (CCD) pilot module operating at 97% recovery. The results of these membrane evaluations were compared based on standard performance metrics (e.g., conductivity rejections and total organ carbon [TOC] rejection), PFAA rejection, and estimated specific energy consumption. Results from this study indicate that tight NF and RO membranes can be used to concentrate PFAS streams by a factor of 33 (97% recovery) with very low permeate PFAA concentrations.