Fate and removal of selected endocrine-disrupting compounds in sewage using activated sludge treatment

The variation and fate of four endocrine-disrupting compounds (EDCs) composed of 4-n-nonylphenol (4-n-NP), bisphenol A (BPA), 17 beta-estradiol (E2) and 17a-ethinylestradiol (EE2) were investigated along treatment units in a sewage treatment plant (STP), China with anaerobic, anoxic and aerobic activated sludge processes. The mean concentrations were 64.8?ng/L (E2), 115.3?ng/L (4-n-NP), 171.5?ng/L (EE2), and 920.7?ng/L (BPA) in the influents, and 22.8?ng/L (E2), 50.9?ng/L (4-n-NP), 49.9?ng/L (EE2), and 84.3?ng/L (BPA) in the effluents. The biological treatment was more effective in removing NP, BPA and E2 from the aqueous phase than the primary treatment, while the latter could effectively remove EE2. Their possible removal mechanisms during the biological treatment with activated sludge were further explored through spiked batch experiments under three oxygen-supplying conditions (anaerobic, anoxic and aerobic). The batch experiments showed that 4-n-NP, E2 and BPA were removed from the aqueous phase through biodegradation. The combination of sludge sorption and biodegradation accounted for the removal of EE2. Anoxic activated sludge showed the most rapid degradation of 4-n-NP, while E2 could be removed most effectively by aerobic activated sludge, and sludge sorption had a remarkable effect on its removal within the initial 15?min of the experiments under three oxygen-supplying conditions.