Impact of Biological Treatment Techniques on Perfluoroalkyl Acids Emissions in Municipal Sewage

摘要

To study the impact of biological treatment techniques on perfluoroalkyl acids (PFAAs) emissions in municipal sewage, high-performance liquid chromatography-tandem mass spectrometry was combined with WAX extraction enrichment to analyze the content and distribution of 14 PFAAs in the influent and effluent of 10 municipal sewage treatment plants that adopted 3 biological treatment techniques including sequencing batch reactor (SBR), oxidation ditch, and A/O-involved processes in Shenzhen, China. The mass flow of PFAAs under different biological treatment techniques was also compared. Results showed that average Sigma PFAAs of the ten sewage treatment plants decreased from 32 to 26 ng/L after treatment, showing no significant difference, but average daily Sigma PFAAs mass flow significantly decreased from 8.1 to 6.1 g/day (p < 0.05). Through treatment, short-chain PFAAs and perfluoroalkyl carboxylic acids (PFCAs) with removal rates of 43 and 29 % decreased significantly (p < 0.01), but long-chain PFAAs and perfluorosulfonates (PFSAs) with removal rates of -0.68 % and -21 % did not. The plants using SBR had an average Sigma PFAAs removal rate of 35 %, comparable to those using A/O-involved processes (27 %). However, the plants using oxidation ditch technique had an average long-chain PFAAs removal rate of -51 %, making their average Sigma PFAAs removal rates reaching -25 %, significantly lower than the other two techniques (p < 0.05).