Distribution And Removal Of Typical Antibiotic Resistance Genes During Sludge Pretreatment And Anaerobic Digestion Processes

Antibiotic resistance genes(ARGs)is considered as a new kind of environmental pollutant,wastewater treatment plants is a major pathway for migration and transformation of ARGs to the environment.In this study,in view of the sludge anaerobic digestion(AD)process,ten typical ARGs in sewage sludge were selected.In this study,quantitative polymerase chain reaction(qPCR)method and high-throughput sequencing method were used.In this study,the distribution and variation of ARGs and microbial community structure were investigated with sewage sludge during alkaline,thermal hydrolysis and ultrasonic pretreatments,and the distribution and variation of ARGs and microbial community structure were compared with different sludge pretreatment-anaerobic digestion processes.The seasonal variation of ARGs in the inlet of sludge and the annual variation of ARGs in the inlet and outlet of sludge anaerobic digestion of municipal sewage treatment plants during long-term operation were conducted.The effect of different pretreatments and pretreatment-anaerobic digestion systems on ARGs and bacterial community were compared.Results showed that thermal hydrolysis pretreatment reduced the absolute abundance of ARGs obviously,but had limited enhancement effect on ARG removal during AD process.Sludge pretreatments improved ARG reduction during the whole pretreatment-anaerobic digestion process,and ultrasonic pretreatment had higher enhancement effects than alkaline and thermal hydrolysis pretreatments.The total ARGs concentration showed significant correlation with 16 S rRNA gene during the pretreatment and AD processes,suggesting that the biomass was a very important influence factor on the variation of ARGs.The three different pretreatments had no significant effects on the bacterial community of raw sludge,while AD significantly changed the microbial communities in sewage sludge.During the period from April 2016 to March 2017,sludge samples of the inlet and outlet of anaerobic digestion of municipal sewage treatment plants in Tianjin were regularly conducted.Results revealed that the absolute abundance of total ARGs in the inlet sludge samples were higher than that in the outlet sludge samples,thissuggests that anaerobic digestion in municipal sewage treatment plants had significant contribution on ARG reduction,and the absolute abundance of ARGs in AD were reduced by 2.7%~69.4%.The variation of the relative abundances of Proteobacteria and Betaproteobacteria in sludge samples during pretreatment-anaerobic digestion tests and anaerobic digestion system of municipal sewage treatment plant had similar trends with the change of total ARGs,suggesting that variation of the absolute abundance of ARGs was significant related with derived from Proteobacteria and Betaproteobacteria in this study.