Degradation of polybrominated diphenyl ethers by a sequential treatment with nanoscale zero valent iron and aerobic biodegradation

BACKGROUND: Polybrominated diphenyl ethers (PBDEs) are emerging persistent organic pollutants. Degradation of PBDEs is a significant challenge owing to their extreme persistence and recalcitrance nature. The objective of this study was to evaluate the effect of a sequential nano‐bio treatment using nanoscale zero‐valent iron (nZVI) and diphenyl ether degrading bacteria Sphingomonas sp. PH‐07 for degradation of PBDEs. RESULTS: In the bacterial tolerance test for determining the maximum endurable concentration of nZVI, the PH‐07 strain was able to grow in the presence of nZVI up to 5 g L−1 in minimal salt medium by using non‐brominated diphenyl ether as growth substrate. Reductive debromination of decabrominated diphenyl ether (deca‐BDE; 1 mg) with nZVI (100 mg per vial) resulted in a 67% reduction of deca‐BDE and produced various intermediates ranging from nona‐BDEs to tri‐BDEs during a 20 day period. Additional experiments with 2,4,4′‐tri‐BDE and 2,4,6‐tri‐BDE as initial substrates revealed that both tri‐BDEs were further debrominated to mono‐BDEs. Following the reductive debromination process, reaction mixtures were aerobically treated with DE‐grown Sphingomonas sp. PH‐07 strain to mineralize the low brominated‐DEs (tri‐BDEs—mono‐BDEs) for additional 4 days. During bacterial treatment, the low brominated‐DEs were biologically degraded to bromophenols and other prospective metabolites. CONCLUSIONS: The nZVI‐biological sequential treatment method was found to be effective for degradation of PBDEs through reductive debromination followed by biological oxidation. This hybrid treatment method may lead to the development of a remediation strategy for highly halogenated environmental pollutants in contaminated sites. Copyright © 2011 Society of Chemical Industry