Occurrence of selected polybrominated diphenyl ethers and 2,2′,4,4′,5,5′ hexabromobiphenyl (bb-153) in sewage sludge and effluent samples of a wastewater-treatment plant in Cape Town, South Africa.

Abstract

The reuse of treated effluent from wastewater treatment plants (WWTPs) as alternative water source for sport-field or landscape irrigation, agricultural, and other industrial purposes is growing significantly. Similarly, the application of treated sludge (biosolid) to agricultural soils is now being considered globally as the most economic means of sludge disposal. However, the presence of emerging organic contaminants in these matrices, including polybrominated diphenyl ethers (PBDEs), which are potential endocrine disruptors, portends a high health risk to humans and the environment in general. In this study, effluent and sewage sludge samples collected from a WWTP were analysed for some selected PBDE congeners (BDE congeners 28, 47, 99 100 153 154 183, and 209) as well as BB-153 using a high-capillary gas chromatograph equipped with an electron capture detector. The sum of the eight PBDE congeners ranged from 369 to 4370, 19.2 to 2640, and 90.4 to 15,100 ng/l for raw water, secondary effluent, and final effluent, respectively. A similar result was observed for sewage sludge samples, which ranged between 13.1 and 652 ng/g dry weight (dw). The results obtained for BB-153 were generally lower compared with those found for most PBDE congeners. These ranged from ND to 18.4 ng/l and ND to 9.97 ng/g dw for effluents and sewage sludge, respectively. In both matrices, BDE 47 and 209 congeners were found to contribute significantly to the overall sum of PBDEs. The reuse of the treated effluent, particularly for agricultural purposes, could enhance the possibility of these contaminants entering into the food chain, thus causing undesirable health problems in exposed subjects.