Biological and bioelectrochemical defluorination of per- and polyfluoroalkyl substances (PFAS)

Che, Shun

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https://hdl.handle.net/2142/115888 Copy

Description

Title

Biological and bioelectrochemical defluorination of per- and polyfluoroalkyl substances (PFAS)

Author(s)

Che, Shun

Issue Date

2022-07-08

Director of Research (if dissertation) or Advisor (if thesis)

Men, Yujie

Doctoral Committee Chair(s)

Men, Yujie

Committee Member(s)

• Liu, Wen-Tso
• Nguyen, Thanh H
• Liu, Jinyong

Department of Study

Civil & Environmental Eng

Discipline

Environ Engr in Civil Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• biodefluorination
• bioelectrochemical defluorination
• PFAS

Abstract

Per- and polyfluoroalkyl substances (PFAS) has attracted increasing attention as a threat to public health and ecosystems due to their strong persistence to environmental degradation, bioaccumulation potential, and plausible toxicity. Efforts have been made to profile the existence of PFAS in various environments and to investigate the biodefluorination and biotransformation of legacy PFAS. However, PFAS consist of over eight thousand individual structures. The biodefluorination of PFAS is far from been well studied and understood. Thus, the primary focus of this study aims to contribute to understanding biodefluorination and biotransformation of PFAS as well as exploring treatment of PFAS at interface between microorganisms and materials, specifically focusing on investigating the defluorination and transformation products, the biotransformation pathways, the responsible microorganisms, and ultimately the responsible genes and enzymes. I studied the biotransformation and biodefluorination of short-chain PFAS in aerobic activated sludge. Eight of fourteen selected PFAS showed removal during the three-day incubation, and four of which showed defluorination. Among them, 3,3,3-trifluoropropionic acid displayed almost complete defluorination within 1 day. The results indicated that carbon-hydrogen bond at alpha carbon is critical for aerobic defluorination, which is consistent with the hypothesis in literature. Reaction pathways were proposed for the PFAS which can be defluorinated by activated sludge. I also investigated the biodefluorination of Cl-PFAS by pure cultures under anaerobic atmosphere. Inspired by the finding that Cl-PFAS could be defluorinated by anaerobic activated sludge, I studied the defluorination of Cl-PFAS with pure isolates. The defluorination pathway and products were less diverse than those in activated sludge. Crude protein extraction and RNA expression analysis were conducted to reveal the possible responsible enzymes for defluorination of 3,5,7,8-tetrachloroperfluorooctanic acid. I explored the treatment technologies of PFAS by investigating the bioelectrochemical defluorination of (E)-perfluoro(4-methylpent-2-enoic acid) (PFMeUPA). Deeper defluorination was observed in bioelectrochemical system than biological or electrochemical system. Transformation products were identified and defluorination pathway was proposed accordingly. 16s rRNA gene sequencing analysis was conducted to analyze the change of microbial community in bioelectrochemical system. Overall, this work advances the fundamental understanding of the fate of various PFAS in engineered environments and opens diverse venues for both fundamental science and engineering applications. Those include investigating structure-activity relationship, identifying the responsible microorganisms/genes/enzymes, and exploring the treatment technologies for PFAS biodefluorination.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Shun Che

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