Correlations And Distribution Patterns Of ARGs,MGEs And Airborne Microbial Communities In Wastewater Treatment Plant

In recent years,the abuse of antibiotics has led to antibiotic residues in bodies of human beings and animals,as well as in environments,which caused the growth and spread of antibiotic resistance bacteria(ARB),including antibiotic resistance pathogenic bacteria.These ARB carrying antibiotic resistance genes(ARGs)can pour into wastewater treatment systems along with human and animal excreta,domestic sewage,swine wastewater and medical wastewater,which made the wastewater treatment systems become important pools of ARB and ARGs.ARB,ARGs as well as pathogenic bacteria in wastewater treatment system can be emitted into air through the aeration process of activated sludge,which can lead to the spread of diseases and cause harmful effects on the health of workers in wastewater treatment plant(WWTP)and the people living around the WWTP.This study aimed to screen for core bacterial community and bioaerosol pollution indicator bacteria around the WWTP air through technologies related to molecular biology and metagenomics,investigate the relationship between ARGs profiles and diversity,mobile genetic elements(MGEs)and bacterial communities in activated sludge and WWTP air,reveal the spatio-temporal difference of bacterial communities and distribution patterns of ARGs and MGEs detected in WWTP air,and provide scientific basis for the control and prevention of risks of ARB and ARGs around the WWTP.The analysis about bacterial communities indicated that the bioaerosol released to the WWTP air through activated sludge aeration can affect the airborne bacterial communities and airborne ARGs distribution patterns in the WWTP significantly.The core airborne bacterial communities around the WWTP were dominanted by Clostridium XI,Sphingomonas and Arcobacter.The genera TM7 and Arcobacter can be considered as indicator of bioaerosol pollution in WWTP air,and can be of significance in indicating the bioaerosol pollution degree of air around WWTP.Significant difference in season and particulate matter size in WWTP airborne bacterial communities have been observed.Generally speaking,the bacterial communities in PM samples showed significant difference at different sampling sites.Compared in winter,the airborne bacterial community above the oxidation ditch in summer suffered more influence of aeration process,and the diversity of airborne microorganisms in summer higher than in winter.In summer,the daily abundance of ARGs and MGEs showed no obvious difference in sampling sites and PM size between activated sludge and WWTP air,but the diversity of ARGs and MGEs in activated sludge were lower significantly than in WWTP air.Compared to dosing room air,office building air and air outside the WWTP,the distribution characteristic of airborne ARGs above the oxidation ditch showed more similar to activated sludge.The distribution patterns of airborne ARGs and MGEs in air outside office building and air outside the WWTP were similar,which suggested that in summer,the office area was barely affected by the bioaerosol pollution of WWTP,and the environmental effect of aeration process would have been both relative minor and local.Statistical analysis showed that the total abundance of ARGs had significant correlation with the total abundance of MGEs(integrons and ISs)in the activated sludge and air collected from the WWTP(r=0.666,p<0.001),indicating that MGEs may play an important role in the horizontal gene transfer of ARGs.MGEs,bacterial communities and environmental factors(such as temperature,wind velocity,PM weight and atmospheric pressure)can affect the distribution characteristics of ARGs together,and the combined effect of MGEs and bacterial communities played the key role in the distribution patterns of ARGs in activated sludge and air of the WWTP.In conclusion,the bioaerosol released to the WWTP air through aeration can affect the air of the WWTP,but the effect was relative minor and local.Spatial-temporal differences of airborne bacterial communities as well as distribution patterns of airborne ARGs and MGEs in WWTP were observed.The total abundances of ARGs and MGEs were correlated with each other.The combined effect of bacterial communities and MGEs was the key factor for the distribution patterns of ARGs.