Study On The Effect Of Compound Quinolone Antibiotics On Denitrification Process Of Groundwater

In recent years,the phenomenon of nitrate pollution and antibiotic pollution in groundwater environment has attracted widespread attention.However,the current impact of compound antibiotic pollution on denitrification is not clear.In order to solve this problem,this study selected representative denitrifying bacteria in groundwater to conduct the combined drug susceptibility test on five typical quinolone antibiotics to evaluate quinolone.Based on the combined effect of compound antibiotics on denitrifying bacteria,the simulation test of the effect of compound antibiotic pollution on the denitrification process was carried out,and the degree of influence of compound antibiotics on the denitrification process of groundwater and the microbial response mechanism were discussed.The main conclusions are as follows:(1)Micro broth dilution method detects the sensitivity of Pseudomonas as the main denitrifying bacteria to five typical quinolone antibiotics in the order of:Enrofloxacin>Ciprofloxacin> Ofloxacin> Lomefloxacin >Norfloxacin.Combined sensitivity test showed that Ofloxacin and Norfloxacin was an irrelevant effect,the effect between Ofloxacin with Ciprofloxacin,Lomefloxacin,Enrofloxacin were antagonism.Norfloxacin and Lomefloxacin were accumulation,and the result of Norfloxacin and Ciprofloxacin or Enrofloxacin was irrelevant.Ciprofloxacin and Lomefloxacin are showed an irrelevant effect,and the effect between Ciprofloxacin with Enrofloxacin was antagonism.The result of Lomefloxacin and Enrofloxacin was irrelevant.(2)The simulation experiment of the effect of compound antibiotic pollution on the denitrification process showed that 159ng/L Lomefloxacin or 503ng/L Norfloxacin uses alone and the combination of the two have different inhibitory effects on the denitrification process in groundwater,which is reflected in each stage of the denitrification process.Lomefloxacin slightly promotes denitrification in the early stage,and later would inhibit it;Norfloxacin always inhibits the denitrification process;The combination of Lomefloxacin and Norfloxacin can inhibit denitrification,and the effect is less than that of Norfloxacin used alone.The inhibitory effect of each system was obtained as Norfloxacin> Norfloxacin+Lomefloxacin> Lomefloxacin,The combined use of Norfloxacin and Lomefloxacin was antagonism.(3)The combination of antibiotics showed antagonistic effect on the number and act-ivity of microorganisms in the denitrification system,and the activity of denitrifying enz-ymes.The dominant denitrifying bacteria were Achromobacter-xylosoxidans-g-norank,Aci netobacter-baumannii-g-Acinetobacter,Pseudomonas-sp-KY and the variation of nos Z and aac.The addition of antibiotics to the denitrification system will have a continuous impact: the number of quinolone antibiotic resistance genes increases,and the resistance of m-icroorganisms will increase in the environment,denitrifying bacteria build defenses again-st antibiotics,and adapt to the environment gradually where low concentrations of antibi-otics exist.As the reaction time increases,the number and active of denitrifying bacteria,denitrifying enzyme activity and microbial community level have a tendency to rise.