Three pilot-scale submerged membrane bioreactors (MBRs) in a local wastewater treatment plant (K, M and Z) were studied with the objective to compare the performance of pre-denitrification MBR systems in eliminating the estrogenic activity of the effluent of primary clarifier. A total of 5 batches of samples, which included influent, effluent, supernatant and sludge from the respective aerobic and anoxic tanks were collected over the span. They were investigated by using the developed solid-phase extraction (SPE) protocol coupled with a modified yeast-based estrogen screen (YES) assay. From the results, it could be seen that M MBR demonstrated the best endocrine disrupting compounds (EDCs) removal efficiency. The fate and behavior of EDCs in MBR systems were fairly understood with estrogenic activity formation dominating in the anoxic tank and removal dominating in the aerobic tank. It is believed that the sorption of EDCs onto the sludge as well as biodegradation of EDCs might be the key mechanisms for the EDCs removal. The low response of YES when dealing with influent samples was mainly due to the inhibition and antagonist effects induced by the influent samples on yeast cells.

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