Degradation of decabromodiphenyl ether (BDE-209) in microcosms mimicking sediment environment subjected to comparative bioremediation strategies.

The aim of this study was to examine bioremediation strategies for BDE-209 contaminated sediments. Sediment microcosms were established to observe anaerobic debromination of BDE-209 under conditions representing three bioremediation strategies: biostimulation, bioaugmentation and natural attenuation. To simulate biostimulation, a defined mineral medium containing both a carbon source (sodium formate) and electron donor (ethanol) was added into sediments. Bioaugmentation was established by enrichment of the sediments using a culture of Dehalobium chlorocoercia strain DF-1, previously shown to dechlorinate polychlorinated biphenyls, to sediments. No amendments were made to the third set in order to represent natural attenuation. The biostimulation, bioaugmentation and natural attenuation strategies resulted in 55.3%, 40.2% and 30.9% reductions in BDE-209, respectively, after 180 days. Nona- through tri-BDEs were observed as products, with 17 PBDE congeners detected in 25 different proposed debromination pathways. At the end of the 180 day incubation period, the products for bioaugmentation, biostimulation and natural attenuation were tri-BDEs, tetra-BDEs and penta-BDEs, respectively. The proposed pathways revealed that meta- and ortho-Br removal were favored in sediments, and that debromination regiospecificity varied with each bioremediation strategy applied. Lastly, pseudo-first-order rate constants for BDE-209 reduction were calculated as 0.0049 d-1, 0.0028 d-1, 0.0025 d-1 for biostimulation, bioaugmentation and natural attenuation, respectively.