Temporal trends of persistent organic pollutants in digested sewage sludge (1993-2012)

In this study, concentrations of selected POPs were measured between 1993 and 2012 in digested sewage sludge from eight municipal waste water treatment plants. Polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-dioxins and furans (PCDD/Fs), which have been banned or restricted for decades, exhibited decreasing trends with apparent half-lives between 9 and 12 years. Polybrominated diphenyl ethers (PBDEs) and long-chain perfluorinated acids showed no clear trend, which reflects the recent introduction of regulations. The analysis of octabromodiphenyl ethers did not reveal indications for reductive debromination of decabromodiphenyl ether; however the analysis of total bromine showed that up to 14% of the total bromine load in sewage sludge originated from PBDEs (average 2%). This is the first study to report temporal trends for more than 20 years of series POPs in sewage sludge.