Dynamics of bacterial community at varying sludge retention time within membrane bioreactor treating synthetic hospital wastewater

The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor (MBR) treating synthetic hospital wastewater. The removal of four pharmaceuticals, namely carbamazepine, estradiol, venlafaxine, and ibuprofen in MBR, was studied at varying sludge retention time (SRT) duration of 100, 45, and 15 days and hydraulic retention time (HRT) of 18 h. The removal of ibuprofen and estradiol was constant at varying SRT; however, a negligible removal of carbamazepine and low removal of venlafaxine was observed (< 20%). The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging. The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing. The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly. For instance, the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs. Moreover, the profile of the dominant genus of the SRTs varied greatly from each other.