Exploring 17α-ethinylestradiol removal, mineralization, and bioincorporation in engineered bioreactors

This research investigated removal, mineralization, and bioincorporation of 17α-ethinylestradiol (EE₂) in membrane bioreactors and conventional bioreactors. When the influent EE₂ concentration was >50 μg/L, the membrane bioreactor (MBR) biomass removed more EE₂ than conventional bioreactor (CBR) biomass in continuous tests, likely because the sorption partitioning coefficients are higher for MBR biomass. Microautoradiography was carried out to investigate the distribution of EE₂ within the aggregates retrieved from the bioreactors, and the results revealed concentration gradients present within the floc. Experiments using radiolabeled ¹⁴C-EE₂ experiments (done with 24.5 μg/L EE₂) showed that EE₂ removal rates and the amount of EE₂ mineralized were similar in MBRs and CBRs. Direct measurements and bioenergetic estimates suggest that EE₂-related carbon is probably incorporated into active biomass, despite the fact that EE₂ was added at a concentration that was much lower than that of the primary growth substrates.