Per‐ and polyfluoroalkyl substances thermal destruction at water resource recovery facilities: A state of the science review

Abstract

Per‐ and polyfluoroalkyl substances (PFAS) are a recalcitrant group of chemicals and can be found throughout the environment. They often collect in wastewater systems with virtually no degradation prior to environmental discharge. Some PFAS partitions to solids captured in wastewater treatment which require further processing. Of all the commonly applied solids treatment technologies, incineration offers the only possibility to completely destroy PFAS. Little is known about the fate of PFAS through incineration, in particular, for the systems employed in water resource recovery facilities (WRRF). This review covers available research on the fate of PFAS through incineration systems with a focus on sewage sludge incinerators. This research indicates that at least some PFAS destruction will occur with incineration approaches used at WRRFs. Furthermore, PFAS in flue gas, ash, or water streams used for incinerator pollution control may be undetectable. Future research involving full‐scale fate studies will provide insight on the efficacy of PFAS destruction through incineration and whether other compounds of concern are generated. Practitioner points Thermal processing is the only commercial approach available to destroy PFAS. Thermal degradation conditions required for destruction of PFAS during incineration processes are discussed. Fate of PFAS through water resource recovery facility incineration technologies remains unclear. Other thermal technologies such as smoldering combustion, pyrolysis, gasification, and hydrothermal liquefaction provide promise but are in developmental phases.

Per- and Polyfluoroalkyl Substances Presence, Pathways, and Cycling through Drinking Water and Wastewater Treatment

“…Interestingly, the porosity of GAC was found to be more influential to PFAS decomposition than the character of its polyaromatic surface. These studies support our earlier hypothesis that PFAS destruction improves with other catalytic materials present (Winchell et al 2021a).…”

“…A possible solution for destroying membrane concentrates, employed by some municipal solid waste facilities, is incineration, which has been used for membrane concentrates from leachate (Ren et al 2020(Ren et al , 2019. Although incineration holds promise for the destruction of PFAS residuals, incomplete mineralization could lead to air emissions (Winchell et al 2021a).…”

“…Both WTPs and WRRFs are in open contact with the atmosphere, and PFAS exist in atmospheric gaseous and particulate matter associated with these processes (Yu et al 2020b;Barber et al 2007;Jahnke et al 2007). Thermal treatments and incineration of wastewater solids also are potential sources of direct gas emissions of PFAS to the atmosphere (Winchell et al 2021a). Once in the atmosphere, FTOHs likely oxidize to yield PFCAs initiated by reaction with OH radicals (Ellis et al 2004).…”

“…Detailed definitions of PFAS-related terminology are available in Buck et al (2011), Dauchy (2019), Pancras et al (2016), and Wang et al (2017). PFAS diversity is tabulated in Winchell et al (2021a), and representative chemical structures are illustrated in Winchell et al (2021b). PFAS comprise a large family of chemicals cataloged across various nomenclatures such as (1) polymeric (including fluoropolymers, perfluoropolyethers, and side-chain fluorinated polymers) and nonpolymeric [including perfluoroalkyl acids and per-/polyfluoroalkylether acids (PFAA), PFAA precursors, and others], most of which are further subcategorized; (2) legacy, transformation products, and emerging PFAS; (3) ultrashort-, short-, and long-chain PFAS; and (4) polar/nonpolar, nonvolatile/ semivolatile/volatile, and neutral/anionic/cationic/zwitterionic PFAS.…”

Utilizing Pine Needles to Temporally and Spatially Profile Per- and Polyfluoroalkyl Substances

“…The fluorochemical manufacturer has not reported production of the chlorofluoroethers, therefore these are likely a component of industrial materials at the airport. Furthermore, in December 2019, the NC fluorochemical manufacturing plant was required to install a thermal oxidizer to control PFAS emissions from the facility (24). This explains the drop in fluoroether abundance from 2017-2018 to 2019-2020, particularly at the sampling site approximately 2 miles from the manufacturing plant (Figure 3).…”