The fate and seasonal variation of several typical endocrine-disrupting chemicals (EDCs), including estrone (E1), 17 beta-estradiol (E2), 17 alpha-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 SIP 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. (C) 2011 Elsevier B.V. All rights reserved.