Effects Of Minocycline Hydrochloride On Water Quality Of Urban Sewage Pipelines And Their Biodegradation

With the increasing use of antibiotic drugs,more and more antibiotic residues enter the urban sewage system,making the urban sewage pipe network the best place for antibiotic accumulation and transfer.However,few people pay attention to the transportation process of antibiotics in the urban sewage pipeline network,and there is still a lack of research on the changes and effects of antibiotics in the pipeline migration process.Based on this kind of phenomenon,the influence of minocycline hydrochloride（Highly effective tetracyclines）on the change of water quality（COD,Total phosphorus,Total nitrogen,etc.）along the sewage pipeline was studied by using the simulation reactor of urban sewage pipeline,and explains the reasons for the change of chemical properties of sewage by analyzing the succession of microbial community structure of sewage.In addition,by screening minocycline hydrochloride-degrading strains,the physical and chemical characteristics and optimal degradation conditions of minocycline hydrochloride-degrading strains were preliminarily explored.The results showed that:（1）Minocycline hydrochloride can be effectively removed in a sewage pipeline environment,and the removal rate during pipeline transportation is as high as 90.8±0.5%.（2）The changes in water quality at each pipe section of the sewage pipe network were affected by minocycline hydrochloride.Although the overall consumption of SCOD and TN has not changed significantly,the consumption of TP,NO₃^--N and the growth of NH₄⁺-N at the front end of the pipeline have been suppressed by minocycline.Among them,the consumption rate of TP decreased from 29.4±1.0%to 3.7±2.3%,the consumption rate of NO₃^--N decreased from 86.3±1.4%to 81.5±1.0%,and the growth rate of NH₄⁺-N in the front of the pipeline decreased from 60.3±1.5%to 18.4±1.3%.The overall process of denitrification was affected.In addition,minocycline hydrochloride also inhibited the reduction of SO₄^2-at the front of the sewage pipeline,reduced the generation of H₂S gas,but promoted the release of CH₄ gas,and increased the risk of explosion in the sewage pipeline.（3）Minocycline hydrochloride reduced the diversity of microorganisms in sewage pipeline,replaced the composition of microbial community structure,and changed the abundance of flora related to the change of sewage quality.Some dominant bacteria,such as Clostridium sensu stricto,Lactococcus,Citrobacter and Macellibacteroides can adapt to the antibiotic environment,the abundance ratio get improved.The activities of Chryseobacterium,Pseudomonas,Acinetobacter,anaerovorax,levilinea,longelinea,candidaus cloacaminas and Rhizobium,which are related to phosphorus consumption and nitrogen consumption,were all inhibited,and the percentage of abundance decreased significantly.The abundance of sulfate-reducing bacteria（SRB）such as Desulfovibrio,Desulfomonile,and Desulfomicrobium increased slightly.At the same time,the proportion of various methanogens in archaea was also affected by minocycline hydrochloride,and the overall number of methanogens slightly increased.（4）Minocycline hydrochloride in sewage pipes is mainly removed by biodegradation.Through screening,purification and other technical means,the high-efficiency degrading strain of minocycline hydrochloride was isolated from the sewage microorganisms and named A-13.Bacteria A-13 is a gram-negative bacterium,and its colony shape is an impermeable white semicircle.Through the biodegradation characteristics test,the optimum temperature and pH for the degradation of strain A-13were determined to be 25℃and 7.0,respectively.