Study On The Characteristics Of Bacterial Resistance In Petrochemical Wastewater Treatment Plants And The Mechanism Of Ketone Stress Resistance

In Recent years,antibiotic-resistant pollution has been clearly listed as one of the emerging threats to public health and ecosystem security.As a new type of pollutant,antibiotic-resistance bacteria（ARB）and antibiotic-resistance genes（ARGs）have been widely found in environmental media such as rivers,lakes,oceans,sediments and soil.Among them,the sewage/wastewater treatment system is an important way for ARB and ARGs to spread and diffuse into the environment.The environmental behavior characteristics of ARGs in sewage/wastewater treatment systems have received extensive attention from domestic and foreign researchers.However,most of the current research are concentrated in municipal sewage treatment plants.Only a few researchers have investigated the distribution and removal characteristics of ARB and ARGs in industrial wastewater treatment systems,and there is still no research on antibiotic resistance pollution in petrochemical wastewater treatment plants.In this study,antibiotic susceptibility experiments and fluorescent quantitative polymerase chain reaction（q PCR）were used to systematically study the distribution characteristics and removal effects of ARB and different forms of ARGs in an actual petrochemical wastewater plant.In addition,based on the detection results of organic matter in the actual petrochemical wastewater,the methyl isobutyl ketone（MIBK）was selected for impact experiments to observe the impact of MIBK on the concentration of ARB and the abundance of ARGs,and further explore its potential mechanism of action.The total absolute concentration of ARB（tetracycline,sulfonamide and ampicillin）in petrochemical wastewater treatment plant is8.45×10²-2.38×10⁵ CFU/m L,and the relative concentration is0.006-0.506;the concentration of sulfonamide ARB in anaerobic-aerobic（A/O）process decreases first and then rises,while the absolute concentrations of tetracyclines and ampicillins in different processes have no obvious fluctuations;the absolute concentration of ARB is in the order of sulfonamides≈ampicillins>tetracyclines;the removal rate of the total amount of ARB in wastewater treatment plants is-0.12-0.63 lgs,and the ARB removal rate in anaerobic tank,aeration tank and sedimentation tank is 0.04-0.21,-0.12-0.22 and-0.41-0.18 lgs.The absolute abundances of ae ARGs and i ARGs in activated sludge are 1.96×10⁷-3.02×10¹⁰ copies/g and 5.22×10⁷-4.15×10¹⁰ copies/g,and the relative abundances are 9.81×10^-5-1.74×10⁰ and 7.21×10^-6-7.46×10^-1;among them,tet M and tet O have the highest abundance(1.57×10⁸-4.15×10¹⁰ copies/g);the same type of intracellular and extracellular ARGs（such as sul II）have significant differences in abundance;the removal rate of i ARGs and ae ARGs by oxygen tank,aeration tank and sedimentation tank is-0.34-0.65,-1.13-0.80 and-1.17-1.21 lgs;the absolute abundance of fe ARGs is 5.90×10⁸-1.01×10¹²copies/L;Biofilm pretreatment-aeration（O/O）,one-stage aeration-two-stage contact oxidation（HO/O）and A/O three wastewater treatment processes have a total removal of-0.02,0.16 and 1.73 lgs for free sul II,the total removal of tet M is 0.07,0.11 and 0.32 lgs.Based on RDA analysis,it is confirmed that tetracycline and ampicillin ARB are positively correlated with Cl^-and COD concentration;sulfonamide ARB is positively correlated with TN and COD concentration;i ARGs and fe ARGs are both significantly positively correlated with heavy metal（especially Zn）concentration;ae ARGs（int I1,tet C and sul II）are significantly positively correlated with TN and COD concentrations.It was observed through bacterial culture experiments that low concentrations of methylisobutanone（0.05 mg/L）first inhibited（1-12 h）and then promoted（24-168 h）ARB growth,while high concentrations of methylisobutanone（50 mg/L）continued to inhibit ARB growth（0.15-2.75 lgs）;Methylisobutanone concentrations of 10,20 and 40 mg/L had no significant effect on ARGs conversion（0.953-1.057 lgs）.Concentrations of 100,200 and 300 mg/L can significantly promote ARGs conversion frequency（4.006-4.495 lgs）;the potential mechanism of methylisobutanone affecting the drug resistance of bacteria is to stimulate the production of reactive oxygen species,promote drug efflux and promote transformation.