Screening Of Oxytetracycline Degrading Bacteria And Study The Enhancement On Aerobic Granular Sludge System

In recent years,due to the rapidly development of livestock and aquaculture industry,tetracyclines were detected frequently in aquatic and soil environment.Oxytetracycline（OTC）,as one of the largest and the most widely used antibiotic,which residue was increased year by year in natural water.Pharmaceutical industry and livestock breeding wastewater which contained OTC feed into the sewage treatment system,sewage treatment plant could not effectively remove the pollutants.Residual drug enters the receiving water with the sewage and participate in water system cycle.It will cause potential harm to the stable and healthy development of the ecological environment.Hence,it’s necessary to improve traditional techniques to change this situation.This study chose OTC from the livestock breeding wastewater as research object.Strains with capable of degrading oxytetracycline were separated from aerobic granular sludge.After expanded culture,bacteria acted as biological fortifiers were added into the GSBR reactor to explore the removal efficiency of the conventional pollutants and target pollutants.And the change of microbial community of aerobic granular sludge was studied from the perspective of molecular biology.This study chose the sludge obtained from the secondary sedimentation tank of sewage plant as the inoculated sludge to acclimate aerobic granular sludge in GSBR reactor for a long time.The mature aerobic granular sludge was light yellow with smooth surface,clear outline and dense structure.Particle size of 2.0～4.0mm granular sludge was more than half of the total sludge volume,with good sedimentation performance,high biological activity,the stable removal of conventional pollutants.10stains with capacity of degrading OTC were separated from the aerobic granular sludge.At last,the strain TJ3 and TJ13 were identified as OTC degradation bacteria.After test,strain TJ3 and TJ13 was Pandoraea and Burkholderia,respectively.And the optimum degrading conditions were confirmed as well.For strain TJ3,it had the best removal efficiency when the p H was 6.0,the temperature was at 30℃,the inoculation size was2%and the substrate concentration was 80mg/L.The sodium acetate was added as additional carbon source could promote the degradation of OTC.For strain TJ13,the removal rate reached highest when the p H was 7.0,temperature was at 30℃,and the substrate concentration was 10mg/L.And the addition of beef extract was conducive to the degradation of OTC.About the strengthen process examination,this study focused on two aspects,which were the effects of different running time and different dosage of biological fortifier on aerobic granular sludge system.The result showed that the removal rate of COD and NH₄⁺-N was the best when the running time was 2.4 hours.About the removal of TP from granular sludge,there was no significant difference under two running times.It could promote the removal of OTC by extending the running time,appropriately.Comparing with the control group,the addition of biological fortifier could improve the removal of conventional pollutants.And the optional dosage should be 1%～2%of effective reactor volume.The microbial diversity of aerobic granular sludge in the strengthen pocess was analyzed by high-throughput sequencing.The results demonstrated that Zoogloea、Tolumonas、Enterobacter and Flavobacterium was the common dominant species when the biological fortifier was added into four reactor.The abundance of dominant species was variational in different operational period.Shorter running time could improve the microbial diversity and the microbial diversity could increas with the reactor operation by Alpha analysis and Beta analysis.