Impact assessment of carbamazepine on aerobic granular sludge: monitoring morphology changes, extracellular polymeric substances production, microbial dynamics and toxicity

Abstract

Aerobic granular sludge (AGS) technology for treating pharmaceutical-contaminated wastewater has sparked a great deal of interest in recent decades. However, the prolonged effect of these pollutants in AGS systems still requires further studies. In this study, an aerobic granular sludge sequencing batch reactor (AGS-SBR) was used to treat synthetic wastewater containing carbamazepine (CBZ) at varying concentrations. The purpose of this study was to evaluate the system performance, monitor the stability of the granular biomass, as well as to assess the system ability to detoxify the contaminated wastewater and to identify potential key-bacterial genera. Results show that the AGS-SBR quickly adapted to the presence of CBZ as the removal of the main nutrients was not negatively affected. Regardless of the observed accumulation of CBZ, wastewater toxicity was reduced by up to 70%. The structure and stability of the AGS were not affected, with larger aggregates prevailing throughout the treatment. Sequencing of the 16S rRNA gene revealed that Thauera, Pseudomonas and Flavobacterium were the most abundant genera and may have played a crucial role in the stability of the system through the production of extracellular polymeric substances (EPS). These genera were also found to have several species that contain CBZ-degrading enzymes. In summary, this study underscores the resilience of AGS-SBR systems in treating CBZ-contaminated wastewater, highlighting the critical role of certain microbial groups for the developed AGS system. The authors suggest further studies aimed at validating the ability of Thauera and Flavobacterium to biodegrade CBZ, as well as optimizing AGS systems through bioaugmentation with the aforementioned genera.