Occurrence, fate and risk assessment of parabens and their chlorinated derivatives in an advanced wastewater treatment plant

In the present study, parabens, p-hydroxybenzoic acid (PHBA) and chlorinated derivatives, were simultaneously determined in wastewater and sludge samples along the whole process in an advanced wastewater treatment plant (WWTP). Nine target compounds were detected in this WWTP, and methylparaben and PHBA were the dominant compounds in these samples. It is noteworthy that octylparaben with longer chain was firstly detected in this work. Mass balance results showed that 91.8% of the initial parabens mass loading was lost mainly due to degradation, while the contribution of sorption and output of primary and excess sludge was much less (7.5%), indicating that biodegradation played a significant role in the removal of parabens during the conventional treatment process. Specifically, parabens were mainly degraded in the anaerobic tank, and PHBA could be effectively removed at high rates after the advanced treatment. However, both biodegradation and adsorption accounted for minor contribution to the removal of chlorinated parabens during conventional treatment process, and they were only scantly removed by conventional treatment (33.9-40.7%) and partially removed by advanced treatment (59.2-82.8%). Risk assessment indicated that parabens and their chlorinated derivatives in second and tertiary effluent are not likely to produce biological effects on aquatic ecosystems.