Evaluating the removal efficiency of emerging contaminants in a gravity-driven membrane bioreactors GD-MBR under various aeration conditions for primary wastewater treatment

Conventional wastewater treatment processes have shown limited efficiency in removing emerging contaminants (EC), including organic micropollutants (OMPs) thus posing risks due to the safe discharge and reuse of wastewater effluent due to the presence of antibiotic-resistant bacteria and antibiotic resistance genes (ARG). Membrane technologies are being considered as alternative wastewater treatment strategies. In this context, gravity-driven membrane bioreactors (GD-MBRs) has been highlighted as a sustainable treatment process due to the low energy consumption. This study evaluates the efficiency of GD-MBR in removing selected OMPs (sulfamethoxazole, carbamazepine, and diclofenac) and the impact on ARGs abundance during the treatment of raw primary wastewater. Three GD-MBRs were operated in parallel at the same time, under different aeration conditions (no aeration, continuous aeration, and intermittent aeration). The OMPs were dosed continuously for all reactors after 78 days of operations. Over time, the efficiency of OMP removal decreased in all reactors. Following the addition of OMPs, the relative abundance of ARGs increased in the membrane biofilms of all three reactors. The no aeration (NA) GD-MBR exhibited the highest removal efficiency for sulfamethoxazole up to 64 %, while exhibiting a higher increase in sulfonamide resistance genes with 2 gene copies/16S rRNA in the permeate on day 105. This study sheds light on the effectiveness of GD-MBRs in mitigating OMPs under varying aeration conditions, offering insights for wastewater treatment strategies using GD-MBR.