Effects of microbial activity on perfluorinated carboxylic acids (PFCAs) generation during aerobic biotransformation of fluorotelomer alcohols in activated sludge

Abstract

Biotransformation of fluorotelomer alcohols (FTOHs) in wastewater treatment plants (WWTPs) can release toxic intermediates and perfluorinated carboxylic acids (PFCAs) to the aqueous environment. However, little information is known about the role of relevant microbial activity (i.e., autotrophs and/or heterotrophs) in biotransformation of FTOHs. Additionally, the dynamics of microbial community in sludge after exposure to FTOHs remain unclear. In the present research, using domestic and industrial WWTP sludge, we performed lab-scale batch experiments to characterize the FTOHs biodegradation property under aerobic condition. Both heterotrophs and the autotrophs were associated with FTOHs biotransformation. However, the microbial activity influenced PFCAs generation efficiency. Autotrophs based on ammonia oxidation (50mgN/L) resulted in more effective generation of PFCAs than heterotrophs based on glucose (200mgC/L) metabolism. Moreover, autotrophs generated more amounts of short-chain PFCAs (carbon number ≤7) than the heterotrophs. The ammonia monooxygenase (AMO) in ammonia oxidizing microorganisms (AOMs) are suggested as responsible for the enhanced generation of PFCAs during FTOHs biotransformation. In the sludge that had been exposed to poly- and perfluorinated alkyl substances in an industrial WWTP, Chlorobi was the predominant microorganisms (36.9%), followed by Proteobacteria (20.2%), Bacteroidetes (11.1%), Chloroflexi (6.2%), Crenarchaeota (5.6%), Planctomycetes (4.2%), and Acidobacteria (3.5%). In the present research, the dosed 8:2 FTOH (12.1mg/L) and its biotransformation products (intermediates and PFCAs) could force a shift in microbial community composition in the sludge. After 192h, Proteobacteria significantly increased and dominated. These results provide knowledge for comprehending the effects of microbial activity on FTOHs biodegradation and the information about interaction between microbial community and the exposure to FTOHs in activated sludge.