Per‐ and polyfluoroalkyl substance removal in carbon‐based advanced treatment for potable reuse

Abstract

AbstractThe persistence of perfluoroalkyl acids (PFAAs) in wastewater effluent highlights the need for active monitoring and targeted removal of these compounds in potable reuse applications. The City of Altamonte Springs' permanent potable reuse demonstration facility, pureALTA, employs a carbon‐based advanced treatment process using multiple treatment barriers to provide potable water that meets state and federal regulatory requirements and health guidelines for unregulated contaminants. The combination of ozonation, biological activated carbon filtration (BAC), ultrafiltration (UF), granular activated carbon adsorption (GAC), and UV advanced oxidation process (UV AOP) showed complete removal of long‐chain PFAAs (perfluoroalkyl sulfonic acids with ≥6 carbons and perfluoroalkyl carboxylic acids with ≥7 carbons) with federal health guidelines, such as perfluorooctanoic acid and perfluorooctane sulfonate in the advanced treated water while maintaining total organic carbon (TOC) levels below 3 mg/L, the regulatory limit in Florida for indirect potable reuse. Ozone, BAC, and UF showed increases in PFAAs to varying levels based on the transformation of precursors. GAC was the critical process for both TOC and PFAA removal; as anticipated GAC media's age defined the extent of removal of short‐chain PFAAs such as perfluoropentanoic acid and perfluorohexanoic acid. Because of regulatory limits on TOC in Florida potable reuse projects and the absence of regulations on short‐chain PFAAs, TOC continues to dictate GAC media change‐out frequency and operating cost. However, the performance control strategy for GAC at pureALTA may change if stringent limits are set for short‐chain PFAAs in the future. As of May 2021, pureALTA has been in operation for more than 4 years and continues to operate, providing an opportunity for continued research and community engagement.Article Impact StatementThe study represents the first pilot‐scale evaluation of perfluoroalkyl acid removal and correlation to total organic carbon in a carbon‐based advanced treatment process for potable reuse in Florida.