BACKGROUND: This study analyzed the effects of carbamazepine, ciprofloxacin and ibuprofen on the behavior of a membrane bioreactor (MBR) system treating urban wastewater that was doped continuously with three different concentrations of this mix of pharmaceuticals under a hydraulic retention time of 6 h. RESULTS: The degradation capacity of these chemicals and the heterotrophic kinetics regarding the organic matter removal were evaluated in the control and doping cycles.CONCLUSIONS: Although the MLSS decreased drastically, these differences were not observed in the organic matter removal as the increase of cell growth rate cancelled out the increase in cell decay rate due to the chemical stress caused by the addition of pharmaceuticals, as shown by the increased organic matter degradation rate from 86.27 mgO 2 L −1 h −1 in the control cycle to values within the limits 183.97 mgO 2 L −1 h −1 and 192.88 mgO 2 L −1 h −1 in doping cycles. The degradation rates were 0.0154, 0.0152 and 0.0160 gS/(( gS in /L)*h*mgMLSS) for carbamazepine, ciprofloxacin and ibuprofen, respectively, involving removal yields higher than 71.9, 88.7 and 94.7% for carbamazepine, ciprofloxacin and ibuprofen, respectively, at the three different concentrations tested. Therefore, MBR technology can be used as a reliable process to significantly reduce this mix of pharmaceuticals without reducing its organic matter removal capacity.

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The start-up phase of a membrane bioreactor (MBR) for municipal wastewater treatment was studied to determine the effect of temperature on the organic matter removal and heterotrophic kinetics. The MBR system was analyzed during four start-up phases with values of hydraulic retention time (HRT) of 6 h and 10 h, mixed liquor suspended solids (MLSS) concentrations of 4,000 mg L and 7,000 mg L in the steady state, and temperature values of 11.5, 14.2, 22.9 and 30.1 °C. The influence of temperature on the biological process of organic matter removal was determined through the Arrhenius equation and Monod model. At the most favorable operation conditions of HRT (10 h) and MLSS (7,000 mg L) corresponding to phase 4, the effect of these variables dominated over the temperature. Heterotrophic biomass from phase 2 (HRT = 10 h, MLSS = 4,000 mg L and T = 30.1 °C) had the highest values of chemical oxygen demand (COD) degradation rate (r), implying less time to remove organic matter and shorter duration of the start-up phase.

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A bench‐scale bioreactor was operated under two different technologies of membrane bioreactor and hybrid moving bed bioreactor‐membrane bioreactor at hydraulic retention time 6–16 h, sludge retention time 6–24 days, and mixed liquor suspended solids 3400–7800 mg L−1. Analyses of their bacterial community structures showed marked differences between the two technologies for global communities but not for dominant phylotypes, and the domination of different bacterial phylotypes for the different operational conditions. Tetrasphaera genus was ubiquitous (1.1%–19.2% relative abundance) in both bioprocesses. Fodinibacter (0.04%–7.75%) was found to positively correlate with other dominant phylotypes, highlighting the relevance of Intrasporangiaceae family in membrane‐based technologies. Oligotypes distribution of dominant phylotypes showed that certain strains were favored at all operational conditions. Linkage with operational conditions determined that the presence/absence of carriers deeply impacted the relative abundance of dominant phylotypes. The results are relevant to discern the effect of operational conditions over bacterial communities in membrane‐based technologies. © 2018 American Institute of Chemical Engineers AIChE J, 65: 536–548, 2019