Comparative Analysis of Influent and Effluent Measurements of Per- and Polyfluoroalkyl Substances (PFAS) at Wastewater Treatment Facilities.

UNLABELLED: Per- and polyfluoroalkyl substances (PFAS) are infamous for their persistence as emerging environmental contaminants. While new treatment technologies are evolving to reduce PFAS at known sites of environmental contamination, the efficacy of traditional wastewater treatment plants (WWTPs) to reduce the suite of PFAS congeners is relatively unknown. The present research used a mass balance approach to assess the apparent removal efficiency of PFAS at a major regional wastewater treatment facility in the Great Lakes region. Since the sewer sheds for this facility are primarily combined, the sampling and analysis considered both dry- and wet-weather events. Samples of influent and effluent were collected and analyzed using solid phase extraction (SPE) and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A significant feature of the present research is the comparison of removal characteristics observed at this facility compared to those presented in previous studies for the most common PFAS compounds found in domestic wastewater, i.e., PFOA, PFOS, PFHxS, PFHxA, PFNA, 6:2FTS, and PFBS. The comparison uses the "apparent removal efficiency" (ARE) which represents the difference between influent and effluent mass divided by the influent mass. While most all the examined WWTPs display a negative apparent removal efficiency for each congener (effluent mass exceeds the measured influent mass of the particular congener), the urban WWTP of the present study has a more positive removal profile. This research provides potential explanations for the measured AREs while noting that the complexity of PFAS transformations as well as the large number of known congeners makes current approaches of estimating removal efficiency fraught with errors.

PRACTICAL APPLICATIONS: Many wastewater treatment facilities are scrambling to better understand how effectively their treatment processes are handling emerging contaminants, including those in the per- and polyfluoroalkyl substances (PFAS) family of analytes. While some of these analytes now have mandated limits for drinking water applications, there are only limited guidelines for PFAS discharges in wastewater effluent. Consultants and design engineers will likely be very interested in the PFAS influent and effluent data contained in this paper and the use of "apparent" removal efficiency to compare the relative treatment efficacy of various plants with contrasting tributary characteristics. New data from one of the largest operating regional wastewater treatment facilities in the US is compared to other plants throughout the US and the world.