Sorption of perfluoroalkyl substances in sewage sludge

Abstract

The sorption behaviour of three perfluoroalkyl substances (PFASs) (perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutane sulfonate (PFBS)), was studied in sewage sludge samples. Sorption reversibility was also tested from desorption isotherms, which were also linear. Desorption parameters were systematically higher than the corresponding sorption parameters (up to six-fold higher), thus indicating a significant degree of irreversible sorption, which decreased in the sequence PFOS > PFOA > PFBS.

Combined leaching and plant uptake simulations of PFOA and PFOS under field conditions

“…Still, both, the Briggs method and the model optimization of this study, estimated a higher value and thus a more efficient plant uptake of PFOS compared with PFOA. According to Table 3, the rate of NER formation is higher for PFOA than for PFOS, which contradicts the current literature on short-term experiments (Chen et al 2016;Milinovic et al 2016). However, since more than 90% of both substances is in the NER pool at the end of the simulation period, there is no apparent difference in absolute NER formation of both substances in this study.…”

“…the distribution coefficient K d ) of PFAAs is positively correlated with the length of their molecular carbon chain (Gellrich and Knepper 2012). In several studies, K d was linearly correlated to the fraction of organic carbon (OC) in soils indicating that OC is the major sorbent material (Milinovic et al 2016;Miao et al 2017). However, these linear correlations might have positive intercepts which can be interpreted as background sorption due to other sorbents such as mineral soil components (Milinovic et al 2016).…”

“…In several studies, K d was linearly correlated to the fraction of organic carbon (OC) in soils indicating that OC is the major sorbent material (Milinovic et al 2016;Miao et al 2017). However, these linear correlations might have positive intercepts which can be interpreted as background sorption due to other sorbents such as mineral soil components (Milinovic et al 2016). Sorption isotherms fitted to experimental PFAAs sorption data are usually of Freundlich type (Milinovic et al 2016), Langmuir type (Hellsing et al 2016) or both (Hansen et al 2002;Ochoa-Herrera and Sierra-Alvarez 2008), whereas some studies found a linear isotherm (Milinovic et al 2016;Ahrens et al 2011) and others non-linear isotherms (Hansen et al 2002) or both (Ochoa-Herrera and Sierra-Alvarez 2008).…”

“…The degree of NER formation was found to be dependent on the K OC (organic carbon normalized sorption coefficient), resulting in a higher fraction of NER of, e.g. PFOS (40-98% after 24 h) compared with PFOA (0-75% after 24 h) in short-time (days) equilibrium batch experiments (Chen et al 2016;Milinovic et al 2016). However, the opposite was reported from a field lysimeter study: after a 4-month leaching experiment, about 20% of PFOS could not be recovered, while PFOA dissipated to about 45% (McLachlan et al 2019).…”

Deep urban groundwater vulnerability in India revealed through the use of emerging organic contaminants and residence time tracers

“…However the trend of high PFOS emissions from Varanasi (by comparing upstream and downstream concentrations, Figure 2d) is consistent, with around an order of magnitude increase in PFOS from 0.003 g L -1 upstream of Varanasi to 0.025 g L -1 downstream. There are many potential sources of PFAS including sewage sludge (Milinovic et al, 2016), waste water (Houtz et al, 2016), discharge from fire protection foams (Guelfo and Higgins, 2013;Houtz et al, 2013;Hu et al, 2016) and landfill sites (Benskin et al, 2012).…”