Microbial and thermal treatment techniques for degradation of PFAS in biosolids: A focus on degradation mechanisms and pathways

Ravinder Kumar; Tewodros Kassa Dada; Anna Whelan; Patrick Cannon; Madoc Sheehan; Louise Reeves; Elsa Antunes

doi:10.1016/j.jhazmat.2023.131212

Microbial and thermal treatment techniques for degradation of PFAS in biosolids: A focus on degradation mechanisms and pathways

J Hazard Mater. 2023 Jun 15:452:131212. doi: 10.1016/j.jhazmat.2023.131212. Epub 2023 Mar 15.

Authors

Ravinder Kumar¹, Tewodros Kassa Dada¹, Anna Whelan², Patrick Cannon³, Madoc Sheehan¹, Louise Reeves⁴, Elsa Antunes⁵

Affiliations

¹ College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia.
² College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia; Townsville City Council, Wastewater Operations, Townsville, QLD 4810, Australia.
³ Mackay Regional Council, Mackay, QLD 4740, Australia.
⁴ Queensland Water Directorate, Brisbane, QLD 4009, Australia.
⁵ College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia. Electronic address: elsa.antunes1@jcu.edu.au.

PMID: 36934630
DOI: 10.1016/j.jhazmat.2023.131212

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals detected in biosolids worldwide, which have become a significant concern for biosolids applications due to their increasing environmental risks. Hence, it is pivotal to understand the magnitude of PFAS contamination in biosolids and implement effective technologies to reduce their contamination and prevent hazardous aftermaths. Thermal techniques such as pyrolysis, incineration and gasification, and biodegradation have been regarded as impactful solutions to degrade PFAS and transform biosolids into value-added products like biochar. These techniques can mineralize PFAS compounds under specific operating parameters, which can lead to unique degradation mechanisms and pathways. Understanding PFAS degradation mechanisms can pave the way to design the technology and to optimize the process conditions. Therefore, in this review, we aim to review and compare PFAS degradation mechanisms in thermal treatment like pyrolysis, incineration, gasification, smouldering combustion, hydrothermal liquefaction (HTL), and biodegradation. For instance, in biodegradation of perfluorooctane sulfonic acid (PFOS), firstly C-S bond cleavage occurs which is followed by hydroxylation, decarboxylation and defluorination reactions to form perfluoroheptanoic acid. In HTL, PFOS degradation is carried through OH^-catalyzed series of nucleophilic substitution and decarboxylation reactions. In contrast, thermal PFOS degradation involves a three-step random-chain scission pathway. The first step includes C-S bond cleavage, followed by defluorination of perfluoroalkyl radical, and radical chain propagation reactions. Finally, the termination of chain propagation reactions produces very short-fluorinated units. We also highlighted important policies and strategies employed worldwide to curb PFAS contamination in biosolids.

Keywords: Biosolids; Gasification; Hydrothermal liquefaction; Incineration; Per-and polyfluoroalkyl substances; Pyrolysis.

Publication types

Review

MeSH terms

Alkanesulfonic Acids* / metabolism
Biodegradation, Environmental
Biosolids
Fluorocarbons* / chemistry

Substances

Biosolids
perfluorooctane sulfonic acid
Fluorocarbons
Alkanesulfonic Acids