Biodegradation of polybrominated diphenyl ethers and strategies for acceleration: A review

Abstract

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants (BFRs), are widely used in various commercial products. PBDEs have attracted increasing attention due to their toxicity and bioaccumulation potential. Biodegradation associated technologies are cost-effective and environmentally friendly for possible removal of PBDEs from the environments. In this review, both aerobic and anaerobic biodegradation of PBDEs and the methods for accelerated degradation are discussed. Generally, the degradation of higher PBDEs (higher degree of bromination) is slower than that of lower PBDEs (lower degree of bromination) under both anaerobic and aerobic conditions. The aerobic degradation pathways of PBDEs include cleavage of aromatic ring, debromination, and hydroxylation, while reductive debromination dominates the initial pathway of anaerobic degradation. A number of methods to overcome the chemical inactivity and low bioavailability of PBDEs for degradation enhancement are discussed, such as the addition of external carbon sources, surfactants and vitamin B12. In addition, coupling of chemical degradation and biodegradation is also reviewed.