Fate of Antibiotic Resistance Genes in Sewage Sludge and Its Mitigation During Anaerobic Digestion

Sewage sludge is a significant reservoir of antibiotic resistance genes (ARGs) in wastewater treatment plants, posing risks when applied to agricultural soils. Anaerobic digestion shows promise in reducing ARGs in sewage sludge, but its efficacy varies. Factors like forms of ARGs, temperature, pH, solids retention time (SRT), and pretreatment methods influence ARG reduction. Thermophilic anaerobic digestion generally outperforms mesophilic anaerobic digestion in ARG removal. The effect of SRT on ARG removal depends on operational factors, temperature, pretreatment method, and ARG subtypes. While pretreatment methods benefit ARG reduction, ARG rebound during subsequent anaerobic digestion is commonly observed. It is necessary to deeply reveal the effects of anaerobic digestion on ARG fate under different operational conditions and the underlying mechanisms, which will be essential for developing strategies to minimize the environmental impact of ARG.