[Effects of Thermal-alkaline and Thermal Hydrolysis Treatments on Antibiotic Resistance Genes in Sludge].

Sewage sludge from urban wastewater treatment plants is an important source of antibiotic resistance gene (ARGs) dissemination into various environmental media. In this study, two treatment methods were employed to treat sewage sludge: thermal-alkaline lysis (60-100℃, pH 10-12) and thermal hydrolysis (140-200℃, 60-120 min). Through metagenomic sequencing and quantitative polymerase chain reaction technology (qPCR), the effects of different treatment conditions on the physicochemical properties of sludge and the removal of ARGs were systematically investigated. In addition, the correlation between ARGs, intI1, and the physicochemical properties of sludge was analyzed in detail. The results indicated that both thermal-alkaline lysis and thermal hydrolysis treatments could break sludge cells, with thermal hydrolysis showing a more significant effect. Moreover, both treatment methods could effectively reduce the abundance of ARGs in sludge under certain conditions. Under thermal hydrolysis conditions at 200℃ for 120 mins, the absolute abundance of ARGs in sludge reached its lowest level of 4.08×106 copies·g-1, and the absolute abundance of intI1 also achieved its minimum value of 1.83×106 copies·g-1 under these conditions. Correlation analysis revealed a significant positive correlation (P < 0.05) between soluble polysaccharides and intI1 under thermal-alkaline lysis conditions. However, under thermal hydrolysis conditions, multiple ARGs and intI1 exhibited significant negative correlations (P < 0.05) with physicochemical indicators such as soluble chemical oxygen demand (SCOD), soluble proteins, and soluble polysaccharides. The removal of ARGs by these different treatment methods was mainly influenced by the treatment conditions and the degree of microbial cell disruption in the sludge.