The Price of Really Clean Water: Combining Nanofiltration with Granular Activated Carbon and Anion Exchange Resins for the Removal of Per- And Polyfluoralkyl Substances (PFASs) in Drinking Water Production

Abstract

The removal of per-and polyfluoroalkyl substances (PFASs) presents a challenge for drinking water providers. Guidelines for PFAS concentrations in final drinking water are regularly updated to ever-decreasing values, and conventional drinking water treatment plants are not designed to remove PFASs. Currently, the most frequently used removal technique, adsorption to granular activated carbon (GAC), is often considered challenging. High-pressure membranes, such as nanofiltration (NF), have been shown to remove PFASs efficiently. However, the creation of a waste stream comprised of at least 10% of the feedwater volume is recognized as a major drawback of this technique. In this study, a NF pilot plant was operated at a drinking water treatment plant in the city of Uppsala, Sweden, for six months. NF removed up to >98% of PFASs and fulfilled other water quality targets, such as the removal of uranium-238, dissolved organic carbon (DOC), and mineral hardness from the raw water. The concentrate from the pilot plant was treated with two different GAC materials and two different anion exchange (AIX) resins in column tests, where the superior performance of AIX over GAC was observed in terms of PFAS removal. PFAS adsorption curves for GAC were found to superimpose each other for the two water types if normalized to the specific throughput of DOC. The application of the freely available PHREEQC model revealed improvement possibilities in terms of resin properties. A cost analysis using the column test results compared GAC filtration to the combination of NF with adsorption materials. Treatment costs were found to be largely dependent on the PFAS drinking water treatment goals and concentrate discharge requirements, which highlight the economic consequences of prevailing guidelines for drinking water and discharge to the environment. The results of this study provide both the scientific community as well as drinking water providers with important insights into the application of NF for PFAS removal during drinking water treatment as well as that mechanistic and economic aspects of NF treatment and the management of the resulting concentrate.

Foam fractionation removal of multiple per‐ and polyfluoroalkyl substances from landfill leachate

“…Proven methods for PFAS removal include adsorption via granular active carbon (GAC), powdered activated carbon (PAC), and anion exchange (AIX) or via size exclusion using reverse osmosis (RO) or nanofiltration (NF) (Appleman et al, 2013; Appleman et al, 2014; Belkouteb et al, 2020; Crone et al, 2019; Du et al, 2014; Franke et al, 2019; Franke et al, 2021; Kucharzyk et al, 2017; McNamara et al, 2018; Ochoa‐Herrera & Sierra‐Alvarez, 2008; Rahman et al, 2014; Senevirathna et al, 2010; Woodard et al, 2017; Zaggia et al, 2016; Zeng et al, 2020) and have been utilized in full‐scale predominantly for drinking water and groundwater treatment. For GAC and AIX adsorption processes, PFAS removal efficiency has been shown to be dependent on the PFAS chain length, functional group, pH, and is typically negatively affected by the presence of dissolved organic matter (DOC) (Dixit et al, 2019; Gagliano et al, 2020; Kothawala et al, 2017; McCleaf et al, 2017; Schuricht et al, 2017; Siriwardena et al, 2019) and other negatively charged ions.…”

Amphiphilic Perfluoropolyether Copolymers for the Effective Removal of Polyfluoroalkyl Substances from Aqueous Environments

“…11,12 Also, the breakthrough of short-chain PFAS for GAC was reported to be rapid, making GAC a challenging technique for long-term PFAS remediation. 13 Membrane filtration, including nanofiltration and reverse osmosis, was also shown to effectively remove PFAS to levels greater that 90%. 14,15 The two filtration methods removed not only both long chains and short chains of PFAS but also other small molecules.…”

Managing and treating per‐ and polyfluoroalkyl substances (PFAS) in membrane concentrates

“…Adsorption technologies, such as GAC, PAC, and AIX, are often coupled with membranes to separate PFAS (Franke et al, 2019, 2020; Murray et al, 2019). GAC and AIX show up to fourfold improved PFAS removal efficiency when applied to treat NF concentrate streams compared with GAC or AIX treatment of the raw water (Franke et al, 2019).…”

“…GAC and AIX show up to fourfold improved PFAS removal efficiency when applied to treat NF concentrate streams compared with GAC or AIX treatment of the raw water (Franke et al, 2019). The cost of GAC and AIX treatment for NF concentrate depends on discharge volume and drinking water treatment goals in the drinking water treatment plant (Franke et al, 2020). Franke et al reported that AIX resins may be more cost‐effective than GAC to treat NF concentrate for many discharge goals.…”