Enhancement of simultaneous antibiotics and antibiotic-resistance genes removal in sewage sludge during hyperthermophilic aerobic fermentation and assessment of the ecological risks of fermentation products following land application

Sludge is a major carrier of antibiotics and antibiotic-resistance genes (ARGs), and the major environmental source of ARGs following its application to land. Antibiotics and ARGs of fermentation products need to be effectively removed before application on land. In this study, antibiotic removal and ARG fate following the application of conventional aerobic fermentation (CAF) and hyperthermophilic aerobic fermentation (HAF) were investigated. HAF exhibited high efficiency in antibiotic degradation, with 89.9% NOR biodegraded during the stage Ⅰ in HAF process. Temperature influenced antibiotic degradation dynamics in HAF to a greater extent than other abiotic factors, and antibiotic reduction in HAF group was negatively correlated with Bacillus abundance (p < 0.01). ARGs and MGEs in the HAF group decreased rapidly at stage Ⅰ and the ARG-removal rate in the HAF group was higher than that in the CAF group. All the bacteria significantly and negatively co-occurred with ARGs, and MGEs were Bacillaceae. Risk Quotients (RQs) for different fermentation product application scenarios in land were evaluated; the RQNOR value of stage Ⅰ was 26.99% less than that of the CAF group under a 20 t/ha amendment rate. Overall, the HAF process could achieve low risk over a shorter time than the CAF process.