Polybrominated diphenyl ethers and organochlorine pesticides in sewage sludge of wastewater treatment plants in China

The concentrations of chemicals in sewage sludge from wastewater treatment plants (WWTPs) may relate to their levels of use and environmental pollution in the region. In this work, sludge samples were collected from 31 WWTPs in 26 cities in China and analyzed for polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). The concentrations of ∑PBDE (sum of congeners 17, 28, 47, 66, 71, 85, 99, 100, 138, 153, 154, and 183) ranged from 6.2 to 57 ng/g (dw). The concentration of decabromodiphenyl ether (BDE-209) ranged from below limit of detection (LOD) to 1109 ng/g (dw) (with a median of 27 ng/g (dw)), and averaged 55% (median 69%) of the total PBDEs. These levels are about 10–100 times lower than those found in Europe and North America. PBDE levels in sludge were not found to depend on the location and capacity of the WWTPs. Concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDTs) and its major degradation products, and hexachlorobenzene (HCB) ranged from below detection limit to 167 ng/g (dw), 11 to 1065 ng/g (dw), and 7.5 to 319 ng/g (dw), respectively. The major DDT degradation products were p,p′-DDE and p,p′-DDD. The major hexachlorocyclohexane (HCH) isomer in sludge is β-HCH, reflecting its higher affinity to solids and resistance to degradation than other isomers.