The impact of process variables on the removal of PBDEs and NPEOs during simulated activated sludge treatment

This work illustrates that the removal of some endocrine-disrupting compounds from sewage treatment works effluent is dependent on parameters such as sludge age, influent concentrations, concentrations of co-pollutants and hydraulic retention time as well as physicochemical properties of the compound. Greater nonylphenol polyethoxylates (NPEO) and polybrominated diphenyl ether (PBDE) removal was observed at a higher sludge age, and it appeared that the enzymes required for NPEO degradation were already present. NPEO degradation was reduced in the presence of the more hydrophobic PBDE compounds as sorption of PBDEs occurred, rapidly reducing available sorption sites for NPEOs. The more hydrophobic NP and PBDEs demonstrated little degradation in comparison to longer-chain NPEO compounds. From this research, it is apparent that the principal environmental risk of PBDE contamination after wastewater treatment is via sludge-disposal routes. Treatment of wastewater containing NPEO surfactants poses environmental risks via two routes: some nonylphenolic compounds may pass through into receiving waters and degradation products such as nonylphenol and short-chain ethoxylate compounds will enter the environment via sludge disposal.