Removal Of Typical Antibiotic Resistance Genes In Municipal Sewage Sludge By Bio-Acidification And Ferrous Oxidation Deep Dewatering Process

Recently,Antibiotic resistance genes?ARGs?,as an important new environmental pollutant,has been becoming an increasingly serious problem and gradually attracted the attention of researchers worldwide.Sewage sludge of wastewater treatment plants?WWTPs?considered one of critical reservoirs for the propagation of ARGs.The ARGs usually tended to be transferred from wastewater to the bio-solids during traditional wastewater treatment processes in the biological treatment units,which causes abundant ARGs increasing in sludge.Therefore,improper disposal of excess sludge may cause secondary pollution of ARGs,which poses a potential threat to the environmental safety and human health.No matter how to deal with excess sludge,all needs to dewater sludge processing in advance in order to reduce the moisture content of sludge as well as reduce its volume.The bio-acidification and ferrous oxidation deep dewatering p rocess has the advantages of low cost,convenient and environment friendly.In this study,we constructed a bio-acidification and ferrous oxidation deep dewatering processing reactor with Acidithiobacillus ferrooxidans XJF8?NCBI Accession:KF378735?isolated from a strip mining pit in the laboratory.Previous studies have shown that this technology can promote the sludge dewatering?moisture content 60%?and realize excess sludge reduction.In this paper,the removal effect of 40 subtypes of typical ARGs?including mobile gene elements?in municipal sewage sludge was investigated by using high-throughput quantitative PCR.The results shown that this process had a great removal efficiency?9.40%⁶8.18%?for the 16 ARGs subtypes that could be detected in the sludge sample,and the best removal efficiency was the mphA-02 gene.The bacterial communities structure of sludge during the stages of process sample was analyzed with 16Sr RNA high-throughput sequencing,and found that after processing,the relative abundance of species from Proteobacteria,Firmicutes and Acidobacteria were increased significantly,in which acid sensitivity and anaerobic bacteria was obviously decreased.To investigate the relationship between environmental factors(p H and Fe²⁺),sludge samples and sludge bacterial community,we used the R logic language tools for RDA analysis.The results shown that p H and Fe²⁺has a significant?P<0.05?effect on the sludge samples and sludge bacterial community,and species from Proteobacteria,Firmicutes and Synergistetes were shown positive relationship with p H.Furthermore,biomass of the Acidithiobacillus ferrooxidans XJF8 at all stages of the process is significantly lowly?less than 0.05%?with quantitative PCR,this result may be due to the growth characteristic of this bacteria as an autotrophic bacterium,but the existence of this bacterium significantly changed the environmental conditions of the processing and affected the sludge bacterial community,which caused the purpose of the target ARGs removal.Therefore,in this study,we used the Spearman correlation analysis to assess the potential relationship between the sludge bacterial community and the target ARGs subtypes.The results shown that the genus belonging to Proteobacteria and Firmicutes might confer the most contributions to the removal of target ARGs subtypes.Finally,the whole genome scanning of the Acidithiobacillus ferrooxidans XJF8 was sequencing,and the gene sequence was blast for the COG,GO,CARD and KEGG databases to obtain the gene annotation information which confer a preliminary understanding for the basic structure and function of this bacterium at the gene level,and would be benefit for the further study of the mechanism of the Acidithiobacillus ferrooxidans XJF8 in this process system and other applications for pollution control.