PBDEs in Class A Biosolids Produced from Thermal Hydrolysis and Anaerobic Digestion Processes

Polybrominated diphenyl ethers (PBDEs) are ubiquitous in the environment and usually accumulate in the biosolids during wastewater treatment. In this study, we measure the impact of changing biosolids stabilization methods on PBDE concentration in biosolids. We investigated PBDEs concentrations in Class A biosolids produced from newly adopted thermal hydrolysis pretreatment and anaerobic digestion (THP-AD) in a Mid-Atlantic nutrient recovery facility. The total PBDE concentration in Class A biosolids was 720 ± 110 μg/kg d.w (n=21), lower than the total PBDE concentration found in previously produced Class B biosolids product from the same facility in 2010. Among the analyzed eight congeners (BDE-28, -47, -99, -100, -153, -154, -183, and -209), BDE-47, -99, and -209 were the most common congeners and contributed to about 87% of the total PBDEs concentration. From Class B to Class A biosolids production, the most prevalent congener was BDE-209, and its concentration was decreased from an average 1500 μg/kg d.w. to an average 240 μg/kg d.w. This congener also contributed less to the total PBDE concentration from 82% to 34%. In addition, despite the varied conditions of initializing a full scale anaerobic digestion system, no significant differences were observed between the startup period and the full-operation period of the THP-AD system.