Pilot-Scale Demonstration of Foam Fractionation and Hydrothermal Alkaline Treatment for PFAS Removal and Destruction in a Municipal Wastewater Stream

Abstract Municipal wastewater treatment plants (WWTPs) are a known focal point for per- and polyfluoroalkyl substance (PFAS) accumulation, transformation, and transport. PFAS from disparate household and industrial sources are conveyed to central WWTPs and often end up in municipal biosolids or in effluent liquids. Treatment of PFAS in a WWTP context is a major technical challenge due to the high flow rates, often low PFAS concentrations, and complexity of the water matrix. Foam fractionation (FF) and hydrothermal alkaline treatment (HALT) are PFAS treatment technologies, capable of concentrating and destroying PFAS, respectively. Foam fractionation leverages the air partitioning propensity of many PFAS to separate these compounds into a concentrated foam, while HALT leverages high temperature and high pH conditions to degrade and defluorinate PFAS. In this study, two continuous flow systems of FF and HALT treated 60,000 L of sludge dewatering pressate as a sequential treatment train at the pilot scale to assess performance metrics in a WWTP context. For the foam fractionation portion, long chain PFAS such as PFOS and PFOA were completely removed, and under the best performing conditions, total measured PFAS were removed by 78%. Following primary fractionation and foamate concentration, a waste product equivalent of one gallon per 490 gallons of water treated was achieved. Subsequently, HALT achieved >99% total measured PFAS destruction and removal in the foamate under the best performing conditions.