| Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants primarily used in the electronics, plastics and textiles industries. Upon use in the so-called "technosphere", many PBDEs eventually pass through wastewater treatment plants (WWTPs), one of the primary interfaces between the technosphere and the aquatic environment. Although several studies have established the majority of influent PBDEs end up in the biosolids fraction, knowledge of the fate of PBDEs in specific treatment stages (particularly those involved in biosolids stabilization) is still lacking. Given that arguments in favor of continued BDE-209 use hinge on its non-toxicity, it is imperative that we understand whether BDE-209 can be debrominated to more toxic and bioavailable congers in WWTPs. Our focus is on the reductive debromination potential of PBDEs in sludge from the Calumet Water Reclamation Plant (CWRP) treating both industrial and domestic waste from Chicago; and Woodridge-Greene Valley waste treatment facility (WGV) treating primarily domestic waste from Dupage County, Illinois.;A method was developed to extract, cleanup and quantify 43 BDE congeners ranging from di- to deca-BDEs. The field phase of this research was comprised of detailed analysis of PBDEs and relevant biosolids parameters throughout the sludge treatment train of both plants. Results indicate that BDE-209 and other BDE congeners are significantly transformed in the thermophilic digester of the WGV, but not in the standard rate digester at CWRP.;Laboratory studies included determination of the potential and rate of reductive debromination in controlled studies using a variety of inhibitors and biostimulation agents with potential "haloprimers" to confirm the WGV results. These laboratory data were used to suggest possible pathway and kinetic rates of reductive debromination in the digester and at other stages in sludge processing. Based upon our results, it has been confirmed that BDE-209 is reductively debrominated to lower brominated congeners under thermophilic digestion. These results suggest the possibility of increased BDE bioavailability, and even toxicity given the known characteristics of the lesser brominated BDE congeners. Finally, debromination kinetic data generated from this study allows predictions to be made of BDE dynamics in various digester formulations using a pseudo-first order kinetic regime. |
