Concentrations and fate of parabens and their metabolites in two typical wastewater treatment plants in northeastern China

Highlights: • 6 parabens and 4 metabolites were studied in two typical sewage systems. • Parabens and metabolites were frequently present in wastewater and sludge. • The A/O and CAST treatment processes are both effective at removing parabens. • Significant environmental emissions were observed in both effluent and sludge. Parabens are widely used in food, pharmaceuticals, and personal care products because they are excellent preservatives. Recently, the environmental fate of parabens has attracted attention owing to their similarity to some endocrine disrupters. Wastewater treatment plants (WWTPs) are both important sinks of parabens discharged from our daily activities and key pollution sources for the environment if the parabens are not completely removed. However, research in this area is scarce, especially in Asia. In this study, 6 commonly used parabens and 4 metabolites were analyzed in wastewater and sludge samples from two typical WWTPs with different treatment processes (the anaerobic-oxic (A/O) and cyclic activated sludge technology (CAST) treatment processes). The average concentrations of parabens in the A/O and CAST treatment processes were 1510 ng/L and 2180 ng/L, respectively, in the influent, and 70.5 ng/L and 19.7 ng/L, respectively, in the effluent. The paraben removal efficiencies in the A/O treatment process were between 56.8% and 100%, which is lower than the efficiencies for the CAST treatment process (97.7% to 100%). The average concentrations of metabolites in the A/O treatment process, which were much higher than paraben concentrations, were 35,200 ng/L in the influent, 334 ng/L in the effluent, and 146 ng/g in the sludge samples. The removal efficiencies for the 4 metabolites were >92% for the A/O treatment process. In total, for the A/O treatment process, 5.07 kg and 16.8 kg of parabens, and 24.4 kg and 16.0 kg of metabolites, were discharged into the environment annually via effluent and sludge, respectively. Overall, the results of this study indicate that the A/O and CAST treatment processes are both effective at removing parabens and their metabolites.