Adaptation responses of microalgal-bacterial granular sludge to sulfamethoxazole

[Display omitted] •Microalgal-bacterial granular sludge (MBGS) could adapt to sulfamethoxazole (SMX).•SMX had little effect on organics, nitrogen and phosphorus removal by MBGS process.•5 and 10 mg/L SMX was effectively removed by MBGS in both light and dark cycles.•Eukaryotes appeared to be less sensitive to SMX than prokaryotes in MBGS systems.•SMX might be disposed by Scenedesmaceae, Rhodocyclaceae and Burkholderiaceae. The presence of widely used sulfamethoxazole (SMX) in wastewater poses a threat to aquatic organisms and humans. Here, the responses of the emerging microalgal-bacterial granular sludge (MBGS) process in treating SMX-containing wastewater were investigated. The results indicated that 1, 5 and 10 mg/L SMX had little effect on the removals of organics and nutrients after an acclimation period of three to five days. SMX reduced intracellular glycogen content of MBGS, while the production of chlorophyll and extracellular polymeric substances tended to be promoted. Furthermore, the potential mechanisms on how MBGS adapted to SMX were deciphered to be the alterations of microbial community structure and function of MBGS. SMX might be degraded intracellularly into a carbon source for microbial metabolism and the SMX degraders were suspected to be Scenedesmaceae, Rhodocyclaceae and Burkholderiaceae. This study suggests that the MBGS process can handle SMX-containing wastewater, advancing knowledge on MBGS for antibiotics degradation.