Effects Of Coal Gasification Slag On The Abundances Of Antibiotic Resistance Genes And The Bacterial Community During Anaerobic Digestion

Antibiotics remaining in the farm induce the production of antibiotic resistance genes（ARGs）,horizontal gene transfer is an important way for ARGs to spread between microorganisms.Anaerobic digestion is the main way to recycle solid waste,but the ARGs in the digestion products will enter the environment with organic fertilizers,increasing the risk of ARGs transmission.In this experiment,solid waste coal gasification slag with rich pore structure was selected as additive.Three different concentrations of coal gasification slag（0,5and 10 g/L）were studied for anaerobic digestion parameters,ARGs,mobile genetic elements and the bacterial community.This paper analyzes the relationship between ARGs and environmental factors,bacterial community,and reveals the effect of coal gasification slag on the reduction of ARGs during anaerobic digestion and the potential removal mechanism.The main results and conclusions are as follows:1.The pH value shows a trend of decreasing first and then rising during anaerobic digestion.After anaerobic digestion,the content of NH₄⁺-N was the lowest in 10g/L coal gasification slag treatment,and the content of NO₃^--N in each treatment was reduced after anaerobic digestion.The addition of 10g/L coal gasification slag can reduce bio-Zn,bio-Cu and COD.2.After the end of anaerobic digestion,the addition of coal gasification slag treatment can effectively reduce the absolute abundance of 8/12 ARGs.The addition of 10g/L coal gasification slag more effectively reduce the absolute abundance of dfrA7,sul2,tetW,ermF and ermQ.The removal rate reached 24.81%-90.48%.In addition,the addition of 10g/L of coal gasification slag more effectively reduces the absolute abundance of intI2 and ISCR1.Therefore,the addition of 10g/L coal gasification slag can reduce the risk of ARGs transmission.3.The dominant bacteria in the anaerobic digestion are Firmicutes,Bacteroidetes,Proteobacteria and Actinobacteria.The change of bacterial phyla is largely due to the changes of the bacterial genera contained.The addition of 10g/L coal gasification slag also has potential human pathogens（Pseudomonas and Enterococcus）during anaerobic digestion.Network analysis indicates that the abundance of genes and host bacteria also showed similar trends during anaerobic digestion,indicating that the reduction of potential host bacteria abundance may cause the reduction of ARGs.RDA analysis indicates that mobile genetic elements are important factors influencing ARGs.The addition of 10 g/L coal gasification slag treatment can effectively reduce the content of COD,bio-Zn and bio-Cu in anaerobic digestion products,and reduce the abundance of ARGs,MGEs and potential potential human pathogens.Environmental factors mainly affect the changes of ARGs indirectly by affecting microorganisms.The decrease of the abundance of potential human pathogens is an important reason for the decrease of ARGs.MGEs are the main drivers of the changes of ARGs.