Evaluation of Perfluorooctane Surfactants in a Wastewater Treatment System and in a Commercial Surface Protection Product

Abstract

The origin and amount of perfluorooctane surfactants in wastewater treatment systems, and the transformation these compounds may undergo during treatment, were evaluated through measurement and experiment. Influent, effluent, and river water at the point of discharge for a 6-MGD wastewater treatment plant (WWTP) were screened for eight perfluorooctane surfactants. N-EtFOSAA was quantified in influent (5.1 +/- 0.8 ng/L), effluent (3.6 +/- 0.2 ng/ L), and river water samples (1.2 +/- 0.3 ng/L), while PFOS and PFOA were quantified in effluent (26 +/- 2.0 and 22 +/- 2.1 ng/L, respectively) and river water (23 +/- 1.5 and 8.7 +/- 0.8 ng/L, respectively). Signals for PFOS and PFOA were observed in influent samples, but exact quantitative determination could not be made due to low recoveries of these two compounds in field spike samples. Although the source of PFOS and PFOA observed in WWTP effluents is not clear, two hypotheses were examined: (1) the highly substituted perfluorooctane surfactants that constitute commercially available fabric protectors can be transformed to PFOS and PFOA during biological treatment in wastewater treatment systems, and (2) the end products themselves are directly introduced to WWTPs because they are present as residual in the commercial mixtures. Biotransformation experiments of 96 h were run to determine whether N-EtFOSE (a primary monomer used in 3M's polymer surface protection products) could be transformed to lesser-substituted perfluorooctane compounds in bioreactors amended with aerobic and anaerobic sludge from the sampled plant. At the end of the aerobic biotransformation experiment, N-EtFOSAA and PFOSulfinate were the only two metabolites formed and each accounted for 23 +/- 5.0% and 5.3 +/- 0.8% of the transformed parent on a molar basis, respectively. Transformation of N-EtFOSE was not observed under anaerobic conditions. A sample of a commercially available surface protection product from 1994 was analyzed and found to contain six of the targeted perfluorinated surfactants, including PFOS and PFOA. These findings suggest transformation of precursors within wastewater treatment is not an important source of these compounds compared to direct use and disposal of products containing the end products as residual amounts.

Evaluation of perfluorinated compounds in seven wastewater treatment plants in Beijing urban areas

“…In previous studies, industrial and commercial wastewaters have been implicated as a likely source of PFCs [5,29]. The existence of PFOA and PFOS in WWTPs suggests that PFOA, PFOS or related precursors are still in use and constantly released to the aqueous system, though the exact source of PFOA, PFOS and other PFCs in the wastewater has not been well defined yet.…”

“…Scientists have proposed that the everyday cleaning of fluorochemicaltreated products in hospitals or shopping malls would be a significant source of PFCs to wastewaters. According to a study of WWTPs conducted in Iowa City, IA [29], care and cleaning of treated surfaces may be a source of PFCs to the WWTPs from down-to-drain disposal. It has also been hypothesized that the highly substituted perfluorooctane surfactants commercially used as fabric protectors can be transformed to PFOS and PFOA, and become a possible source of PFCs in the wastewater.…”

“…Boulanger et al have testified that perfluorooctane sul-fonate potassium salt (PFOSulfinate) and perfluorooctanesulfonylethylamide (N-EtFOSA), as well as several other precursors, may be transformed to PFOS during the wastewater treatment [29]. This could result in higher concentrations of PFOS in effluents.…”

Congener specific organic carbon normalized soil and sediment-water partitioning coefficients for the C1 through C8 perfluoroalkyl carboxylic and sulfonic acids

“…PFAs have also been studied in municipal wastewater treatment plants (WWTPs) [7,33,37,42,43,[48][49][50]64,69,80,[136][137][138][139][140][141] where sorption of contaminants to organic matter and settling with particulates in grit chambers, trickling filters, rotating biological contactors, and primary/secondary clarifiers, as well as sorption to activation carbon if this polishing step is present, is a major removal process from the final effluent stream. Although it has been previously noted that a means of estimating K oc values for the C 1 through C 8 PFAs would be valuable in better understanding PFA profiles within WWTPs, [137] the potential range of PFA precursors that are subject to biological and physicochemical degradation into PFAs (e.g., perfluoroalkyl sulfonamides, fluorotelomers, etc.)…”

“…in the wastewater influent (as well as in soils) is vast. [136,[140][141][142][143][144][145][146] This issue makes source apportionment and mass balances nearly impossible given our current limited knowledge regarding congener specific kinetic and thermodynamic parameters for degradation and partitioning. A similar caveat must be applied to ground and pore water modeling of PFAs.…”