Succession of bacterial communities during a plant-scale hyperthermophilic composting of sewage sludge

Composting is widely applied in recycling ever-increasing sewage sludge. However, the insufficient elimination of antibiotics and antibiotic resistance genes (ARGs) in conventional compost fertilizer poses considerable threat to agriculture safety and human health. Here we investigated the efficacy and potential mechanisms in the removal of antibiotics and ARGs from sludge in hyperthermophilic composting plant. Samples were collected at various time points during hyperthermophilic composting. Our results demonstrated that the hyperthermophilic composting led to a complete elimination of antibiotics and potential pathogens, as well as a removal of 98.8% of ARGs and 88.1% of mobile genetic elements (MGEs). The enrichment of antibiotic-degrading candidates and related metabolic functions during hyperthermophilic composting indicated that biodegradation played a crucial role in antibiotic removal. Redundancy analysis (RDA) and structural equation modelling (SEM) revealed that the reduction of ARGs was attributed to the decline of ARG-associated bacteria, mainly due to the high-temperature selection. These findings highlight the feasibility of hyperthermophilic composting in sludge recycling and provide a deeper understanding of its mechanism in simultaneous removal of antibiotics and ARGs.