Influences of solid retention time, nitrification and microbial activity on the attenuation of pharmaceuticals and estrogens in membrane bioreactors

• Removal of gemfibrozil, ketoprofen, clofibric acid, and EE2 were dependent upon SRTs in an aerobic MBR.
• Removal of gemfibrozil, diclofenac, bezafibrate, ketoprofen, pentoxifylline, and EE2 were influenced by nitrification.
• Sorption was the dominant mechanism for the removal of phenacetine, acetaminophen and caffeine.
• Carbamazepine was found to be recalcitrant to aerobic biological wastewater treatment.

This study investigated the influences of solid retention time (SRT), nitrification, and microbial activity on the attenuation of pharmaceuticals and estrogens and the total estrogenic activity, using identical bench-scale membrane bioreactors. Phenacetine, acetaminophen, pentoxifylline, caffeine, bezafibrate, ibuprofen, fenoprofen, 17β-estradiol, and estrone were effectively attenuated even at short SRT (8 d). However, the attenuation efficiencies of gemfibrozil, ketoprofen, clofibric acid, and 17α-ethinylestradiol were dependent upon SRTs (20 and 80 d). Some acidic pharmaceuticals (gemfibrozil, diclofenac, bezafibrate, and ketoprofen) and 17α-ethinylestradiol were partially degraded by nitrification. Relatively high removal efficiencies were observed for 17β-estradiol and estrone (natural estrogens) compared to 17α-ethinylestradiol (synthetic estrogen) when nitrification was inhibited. Most of selected pharmaceuticals were not significantly attenuated under presumably abiotic conditions by adding sodium azide except phenacetine, acetaminophen, and caffeine. In this study, carbamazepine was found to be recalcitrant to biological wastewater treatment using membrane bioreactors regardless of the change of SRTs and microbial activity.

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