Evaluating the effect of antibiotics on aerobic granular sludge treatment of pharmaceutical wastewater

Aerobic granular sludge (AGS) has been widely applied in pharmaceutical wastewater treatment due to its advantages such as high biomass and excellent settling performance. However, the influence of commonly found antibiotics in pharmaceutical wastewater on the operational efficiency of AGS has been poorly explored. This study investigated the effects of tetracycline (TE) on AGS treating pharmaceutical wastewater at room temperature and analyzed the related mechanisms. The results demonstrate a dose-dependent relationship between TE's effects on AGS. At concentrations below the threshold of 0.1 mg/L, the effects are considered trivial. In contrast, TE with more than 2.0 mg/L reduces the performance of AGS. In the 6.0 mg/L TE group, COD, TN, and TP removal efficiencies decreased to 72.6–75.5%, 54.6–58.9%, and 71.6–75.8%, respectively. High concentrations of TE reduced sludge concentration and the proportion of organic matter in AGS, leading to a decline in sludge settling performance. Elevated TE concentrations stimulated extracellular polymeric substance secretion, increasing polymeric nitrogen and polymeric phosphorus content. Intracellular polymer analysis revealed that high TE concentrations reduced polyhydroxyalkanoates but enhanced glycogen metabolism. Enzyme activity analysis disclosed that high TE concentrations decreased the activity of key enzymes associated with nutrient removal.