(681d) Effect of Ultrasonic Pretreatment on Anaerobic Digestion to Remove Antibiotic Resistance Genes

Water resource recovery facilities (WRRFs) are crucial environmental sites where antibiotic resistance genes (ARGs) pose significant risks to human health. Anaerobic digestion (AD) is a common method used in WRRFs to manage organic waste and produce biogas, offering a potential means to mitigate ARG levels in sewage. Pretreatment strategies, such as ultrasonic (US) pretreatment, have been explored to enhance organic matter degradation and potentially improve ARG removal during AD. This study aimed to assess the impact of different durations of US pretreatment on the fate of ARGs in waste sludge. Our hypothesis was that US pretreatment could disrupt organic matter and microbial cells, thereby influencing ARG fate. Experiments were conducted using batch anaerobic reactors, wherein sludge from a WRRF in Mt Pleasant, Michigan, USA, underwent US pretreatment for varying durations (30, 40, and 60 minutes) before a 30-day digestion period. The relative abundance of ARGs (sul1, sul2, tetW, tetA, tetO, ermF, and aac(6')-lb) and mobile genetic elements (MGEs) (int1, int2, and tnpA) was assessed before and after US pretreatment, as well as after-AD, using quantitative polymerase chain reaction (qPCR). Results demonstrated a significant reduction in most detected ARG subtypes after US pretreatment, indicating potential disruption of cell structures and sludge integrity. Moreover, the relative abundance of studied MGEs showed a notable decrease after US pretreatment, suggesting limited horizontal gene transfer (HGT) events during this process. Subsequent AD further reduced the relative abundance of ARG subtypes, with the highest removal observed in samples subjected to US pretreatment for 45 minutes. Overall, these findings underscore the effectiveness of US pretreatment in reducing sulfonamide, tetracycline, macrolide, integrons, and transposase in sewage sludge, with optimal results achieved with a 45-minute US-AD treatment.