Cultivation Of Aerobic Granular Sludge And Fate Of Antibiotic Resistance Genes Under Antibiotics Pressures

Due to the wide application of antibiotics in recent decades,the types and concentrations of antibiotics detected in wastewater gradually increase,sulfonamides,macrolides become the most common types of antibiotics in sewage.The presence of antibiotics also imposes strict requirements on the traditional biological treatment process.Aerobic granular sludge(AGS)is a kind of special microbial aggregate formed by self-aggregation of activated sludge.Because of its special spherical structure,high biomass and impact resistance ability,it has become a research hotspot in the fields of municipal wastewater and industrial wastewater treatment.Based on this,this paper set up three groups of sequencing batch activated sludge reactors(SBR),R0,R1,R2,domesticated cultivation of aerobic granular sludge under different concentrations of sulfadiazine(0 ppb,10 ppb,1000 ppb)pressure,to explore the influence of antibiotic in granulation process,AHLs mediated quorum sensing,antibiotic resistance genes(ARGs)and community structure.The AGS obtained from domestication culture was used to treat high-concentration antibiotic wastewater to explore the treatment effect of this culture method on refractory antibiotic wastewater.The main conclusions are as follows:(1)During the granulation period,the presence of sulfadiazine(10 ppb)at a lower concentration accelerated the formation of denser particles.Small particles were formed at 10 days(R1,SVI30 was 38 mL/g with a particle size of 258 ?m),20 days(R0,SVI30 was 29 mL/g with a particle size of 259 ?m),and 25 days(R2,SVI30 was 47 mL/g with a particle size of 321 ?m),respectively.The final particle density was R0(19.4 g·VSS/L),RI(29.7 g·VSS/L),and R2(21.6 g·VSS/L).On the other hand,the persistent sulfadiazine pressure changed the microbial community structure,and the abundance of EPS producers and AHLs producers increased in the presence of antibiotics,which also led to higher concentrations of AHLs in EPS and EPS.It was also found that the presence of sulfadiazine did increase the corresponding ARGs,including the abundance of sull and sul2.In addition to the enrichment of sulfa resistance genes,enrichment of RND efflux pump gene(adeF,mexD,amrB,etc.)is regarded as a combination of microbial community and quorum sensing(QS),it also led to the resistance mechanism type from antibiotic inactivation to the antibiotic replacement and antibiotic efflux of transformation.The network correlation analysis indicated that 19 bacteria belonging to the 3 phylum might be potential hosts for 15 ARGs.In addition,we also found that QS were closely related to the microbial community and the transfer of ARGs.Azoarcus,Burkholderia and Pseudomonas were not only possible producers of AHLs,but also potential hosts of ARGs.Gemmobacter and Leadbetterella were found to be associated with intracellular C12-HSL and were also identified as potential carriers of adeF and mexD.(2)AGS cultured in the presence of low concentrations of antibiotics(10 ppb)was used to treat high concentrations of antibiotic wastewater.In terms of pollutant removal,COD removal rate is relatively stable,maintaining between 80-85%.The removal rate of nitrogen can reach more than 60%after 30 days.At the end of operation,the removal rate of sulfadiazine(SD)and trimethoprim(TMP)reached 99%and erythromycin(ERY)was 70%.Although the granules were broken in the process of operation,it still takes the granule as the main body and has good sedimentation performance,indicating that the acclimated granules can operate stably in the high-concentration antibiotic wastewater.Compared with the control reactor,it was found that high concentration of antibiotics inhibited the secretion of EPS.Sulfa resistance gene(sull increased by 9 times,sul2 increased by 6 times),erythromycin resistance gene(ermB)increased by 6 times.The number of antibiotic resistant bacteria in the effluent from the reactor treating antibiotic wastewater was much higher than that of the control group.This also warns that in practical application,although aerobic particles can be used to treat antibiotic wastewater,the effluent should be taken seriously.