Distribution And Control Of Antibiotic Resistance Genes In Antibiotic Production Wastewater Treatment System And Urban Wastewater Treatment Plant

As emerging pollutants,antibiotic resistance genes(ARGs)can be horizontally transferred into human pathogenic bacteria,which have been serious threat to human health.Studies have shown that the antibiotic production wastewater(APW)treatment system and urban wastewater treatment plant(UWTP)are huge pollution sources and repositories of ARGs in environment.As major antibiotics producer,ARGs have been paid more and more attention by domestic and foreign governments.Up to now,there are few reports on the distribution of antibiotic resistance genes in the working processes of APW treatment system and UWTP.This paper systematically investigated the occurrence and abundance of ARGs(tetracycline resistance genes(tet genes)?sulfonamide resistance genes(sul genes)?-lactam resistance genes(bla genes))in an APW treatment systems and a UWTP in City Shijiazhuang of Hebei Province,by PCR and real-time quantitative PCR(qPCR)assay.The distribution of ARGs was briefly analyzed,from the perspective of horizontal transfer(intl1).The effects of ozone and thermal hydrolysis as pretreatments of sludge anaerobic digestion process to control ARGs were explored.The main results are as follows:(1)ARGs in effluent,dewatered sludge of antibiotic production wastewater treatment system were 0?1.3×1017copies/d,2.6×1014?5.6×1016copies/d,respectively.And the total emissions of ARGs were increased by 120.10%?96607.07%(except blaTEM),of which the discharge of tet genes,sul genes,blaTEM through effluent reached 67%,82%and 80%of the total emissions,respectively,higher than the discharge through dewatered sludge.From the perspective of relative abundance,compared with influent,most ARGs abundance in effluent increased(blaTEM excepted),and the relative abudance of ARGs between wastewater and sludge had no significant difference(P>0.05),of which sul,tet gene abundance could reach the magnitude of 10-1.In addition,the abundances of intIl in the system(8.24×10-3±2.19×10-4?1.44×100±1.24×10-2)were higher than that of most ARGs of corresponding samples.All the other 6 ARGs,except blaTEM,were significantly correlated with intll(P<0.03).(2)ARGs in effluent,dewatered sludge in UWTP were 0?5.34×1015copies/d,0?4.31×1018 copies/d.And the total emissions of ARGs were reduced by 69.69%?98.08%,of which the discharge of ARGs through dewatered sludge reached more than 99%.From the point of relative abundance,the abundance of ARGs in effluent decreased by 0.3?1.74 orders of magnitude compared to influent,which mainly attributed to the primary treatment and tertiary treatment.Besides,the abundances of intIl(3.33×10-2±1.76×10'3?6.01×10-1±2.83×10-2)were higher than that of sul1 and tetA,which were the highest ARGs in corresponding samples.And in addition to blaTEM and tetW,all the rest ARGs were significantly correlated with intll(P<0.05).(3)The abundances of ARGs were decreased by?0.5 and 1.6?4.7 in pharmaceutical sludge and 0.2?0.7 and 1?3 in sewage sludge after pretreatments of ozone and thermal hydrolysis.Compared with anaerobic digestion(AD)of raw pharmaceutical sludge,ARGs in AD after thermal hydrolysis decreased by 0.4?2.6 orders of magnitude(blaNDM-1 had no significant changes);some ARGs in AD after ozone increased.In sewage sludge,the tetA,tetG,tetW,tetX increased in AD both after thermal hydrolysis and ozone,other ARGs decreased no more than 1 order of magnitude.From the perspective of relative abundance,most ARGs of pharmaceutical sludge(except blaNDM-1 and sul2)in AD after thermal hydrolysis were 0.2-1.8 orders lower than that in AD after ozone.Besides,the abundances of some ARGs in sewage sludge increased in AD both after thermal hydrolysis and ozone.