Fate of polybrominated diphenyl ethers during wastewater treatment/polishing and sludge stabilization/disposal

Large quantities of polybrominated diphenyl ethers (PBDEs) have been used as flame retardants in clothing and plastic products since the 1970s. A small fraction of the PBDEs in manufactured products subsequently enters municipal wastewater. Nevertheless, the resistance of these compounds to chemical and biochemical transformations provides opportunities for accumulation in sediments that are in contact with wastewater effluent and agricultural soils that are amended with biosolids derived from wastewater treatment. Balances developed for PBDE congeners indicate that conventional wastewater treatment processes and soil infiltration of treated wastewater in recharge operations do not discriminate significantly among the major congeners in commercially available PBDE products. Accumulation of PBDEs at near part-per-million levels was measured in the surface sediments at the Sweetwater Recharge Facility in Tucson, Arizona, during 10-15 years of operation. Half-lives for loss of major PBDE congeners from sediments were decades or longer. Local agricultural soils amended with biosolids over a 20-year period showed similar accumulation of PBDEs. The widespread use of PBDEs in commercial products, compound persistence, and toxicity indicate that additional effort is warranted to better understand fate-determining processes for PBDEs in the environment.