Sustainable remediation of aquatic sediments contaminated with polybrominated diphenyl ethers and hexabromocyclododecane

Demirtepe, Hale
The most widely used brominated flame retardants (BFRs), namely, polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) are persistent organic pollutants that pose great risk to human health and the environment. This study aims to investigate degradation of PBDEs and HBCDD contaminated aquatic sediments via biotic and abiotic remediation strategies. In order to obtain an indication of use of these BFRs in Turkey, urban and industrial wastewater treatment plant sludges were sampled, yielding Σ22PBDE concentrations between 66.93-2.46x107 ng/g dw, and total-HBCDD ranging from 13.1-616.2 ng/g dw. Results indicated clear evidence of use of BFRs in Turkey. Sediment microcosms were operated for degradation of BFRs to simulate biostimulation (via addition of carbon and electron source), bioaugmentation (via addition of dechlorinating culture) and natural attenuation (no extraneous substance). Both BDE-209 and gamma-HBCDD microcosms showed the highest degradation rate during biostimulation with pseudo-first-order rate constants of 0.0049 d-1, and 0.0542 d-1, respectively. BDE-209 bioaugmentation microcosm yielded the greatest extent of debromination, with tri-BDEs detected at the end of incubation. Identification of 20 debromination pathways indicate preferential Br loss from ortho and meta positions. On the other hand, HBCDD natural attenuation and bioaugmentation microcosms showed no statistically significant difference. Abiotic degradation of BFRs was investigated via catalyzed hydrogen peroxide propagations. The most successful application was through fill-and-draw treatments yielding up to 31.8%, 83% and 93.9% removal of BDE-209, BDE-99, and HBCDD, respectively. BDE-209 and BDE-99 biostimulation mesocosms, with reduced amount of biostimulating agents, showed on average 0.0012 d-1 and 0.0020 d-1degradation rates, respectively. Also, changes in debromination pathways compared to microcosms were observed, revealing the impact of amount of biostimulators supplied in sediments. Finally, all four remediation strategies studied under laboratory conditions were evaluated from the perspective of sustainable remediation principles. 


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Citation Formats
H. Demirtepe, “Sustainable remediation of aquatic sediments contaminated with polybrominated diphenyl ethers and hexabromocyclododecane,” Ph.D. - Doctoral Program, Middle East Technical University, 2017.