Fate and seasonal variation of endocrine-disrupting chemicals in a sewage treatment plant with A/A/O process

The fate and seasonal variation of several typical endocrine-disrupting chemicals (EDCs), including estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), estriol (E3), bisphenol A (BPA) and 4-nonylphenol (NP), were investigated in a municipal sewage treatment plant (STP) employing an anaerobic/anoxic/oxic (A/A/O) process located in Beijing, China by monitoring their concentrations in both wastewater and activated sludge in four seasons throughout 2009. Results indicate that in summer, the examined STP could effectively remove 75.4% of E1 and more than 90% of all other studied EDCs from the wastewater. The biodegradation in the A/A/O process was the primary removal mechanism. Moreover, the removal of EDCs from the wastewater in the A/A/O bioreactor and their concentrations in the solid phase of return sludge exhibited an obvious seasonal fluctuation. The concentrations of EDCs in the effluent and return sludge were much higher in winter and spring than in summer and autumn, which was closely related to the microbial activity and the concentration of mixed liquor suspended solids (MLSS). Therefore, this study may raise a particular concern regarding the removal of EDCs from wastewater and the disposal of excess sludge in cold seasons.

Seasonal variation of the concentrations of studied EDCs in the solid phase of return sludge.Figure optionsDownload as PowerPoint slideResearch highlights
► EDCs were simultaneously analyzed in both wastewater and activated sludge.
► EDCs were effectively removed in summer mainly via biodegradation.
► The removal of EDCs in wastewater by A/A/O showed significant seasonal fluctuation.
► The excess sludge contained a much higher level of undegraded EDCs in cold seasons.