Effects of the antibiotics trimethoprim (TMP) and sulfamethoxazole (SMX) on granulation, microbiology, and performance of aerobic granular sludge systems.

This work assessed the effect of the antibiotics trimethoprim (TMP) and sulfamethoxazole (SMX) on the granulation process, microbiology, and organic matter and nutrient removal of an aerobic granular sludge (AGS) system. In addition, after the maturation stage, the impact of the redox mediator anthraquinone-2,6-disulfonate (AQDS) (25 µM) on the biotransformation of the antibiotics was evaluated. The reactor R1 was maintained as a control, and the reactor R2 was supplemented with TMP and SMX (200 µg L-1). The ability to remove C, N, and P was similar between the reactors. However, the structural integrity of the AGS was impaired by the antibiotics. Low TMP (∼30%) and SMX (∼60%) removals were achieved when compared to anaerobic or floccular biomass aerobic systems. However, when the system was supplemented with AQDS, an increase in the removal of TMP (∼75%) and SMX (∼95%) was observed, possibly due to the catalytic action of the redox mediator on cometabolic processes. Regarding the microbial groups, whereas Proteobacteria and Bacterioidetes increased, Planctomycetes decreased in both reactors. However, TMP and SMX presence seemed to inhibit or favor some genera during the formation of the granules, possibly due to their bactericidal action.

Aerobic granular sludge: Cultivation parameters and removal mechanisms.

Aerobic granular sludge (AGS) has been the focus of many investigations, and the main parameters responsible for AGS formation are hydrodynamic shear force, short periods and feast-famine cycles. However, some other parameters are associated with AGS maintenance after long periods of operation. This review evaluates the parameters responsible for AGS formation and maintenance and some reference values are proposed. In addition, some discussions are addressed about the main metabolic pathways that AGS uses for the removal of some compounds, such as nutrients, organic matter, dyes, recalcitrant compounds, among others. Finally, the main microbial groups present in the AGS and their respective functions are discussed. It is also highlighted that many parameters that are taken as reference currently for AGS cultivation and maintenance can be optimized for energy savings, implementation costs, among others, as well as a greater recovery of resources during wastewater treatment, within the scope of the biorefinery concept.