Study On Interaction Mechanism Between Cefotaxime Sodium And Microorganisms In Normal Temperature Anaerobic Antibiotic Wastewater Treatment Process

Antibiotic pharmaceutical wastewater is an important pollution source of environmental antibiotics because of its complex composition,high concentration of pollutants such as organic matter,sulfate and ammonia nitrogen,as well as up to thousands of mg/L residual drug active ingredients.Anaerobic process does not require oxygen supply and energy consumption and can generate recoverable methane energy by decomposing organic matter in wastewater.Anaerobic membrane bioreactor（An MBR）process has good application potential in antibiotic wastewater treatment.In this study,cefotaxime sodium pharmaceutical wastewater was taken as the treatment object.First,the interaction between cefotaxime sodium and anaerobic sludge was verified through batch test.The comprehensive efficiency of An MBR,An SBR and An CBR processes（organic matter removal,methane production,change of volatile fatty acid（VFA）,cefotaxime sodium removal and decomposition products,microbial population structure and resistance genes）was systematically investigated.The main research results are as follows:（1）Within 48 h,1000 mg/L cefotaxime sodium hardly hydrolyzed in pure water at 15 ℃,but 5.2% and 25.5% hydrolyzed at 25 ℃ and 35 ℃,respectively.The variation trend of the total concentration of cefotaxime sodium in simulated wastewater and simulated wastewater +anaerobic inactivated sludge accords with pseudo first-order kinetics,and its rate constant is0.065 h-1 and 0.050 h-1,and its half-life is 10.7 h and 13.9 h,respectively.The variation trend of cefotaxime sodium total concentration in simulated wastewater + anaerobic activated sludge was divided into descending stage and rising stage.The descending stage was in line with second-order kinetics and the half-life was 0.10 h.Cefotaxime sodium and its decomposition products have inhibitory effect on anaerobic microorganisms,but cefotaxime sodium and its decomposition products have antagonistic effect on inhibition.（2）Low concentration（≤10 mg/L）cefotaxime sodium had no significant inhibition effect on the total COD removal of An MBR,and 1000 mg/L cefotaxime sodium reduced the total COD removal rate of An MBR from 92.0% to 51.7% under normal condition.The HIGHEST COD removal rate of An SBR was 79.6% under 100 mg/L cefotaxime sodium load,and the lowest was 33.3% under 1000 mg/L cefotaxime sodium load.Low concentration（≤10 mg/L）cefotaxime sodium had no significant inhibition effect on An CBR COD removal,and 1000 mg/L Cefotaxime sodium reduced the total COD removal rate of An CBR from 93.1%to 79.9%.The addition of carbon fiber biofilm increased the activities of acid and methanogenic bacteria under the loading of 1000 mg/L Cefotaxime sodium.The higher the sludge concentration is,the more likely it is to cause the rise of the transmembrane pressure difference in An MBR.Cefotaxime sodium enhanced the effect of sludge concentration on the rise of transmembrane pressure difference.（3）The mass to charge ratio of decomposition products I～VI of cefotaxime sodium can be detected in anaerobic reactor,pure water and simulated wastewater.The decomposition pathway of cefotaxime sodium is affected by solution salinity,p H and microbial action.Cefotaxime sodium mainly inhibited the activity of acetic acid producing bacteria,thus reducing the available substrate of methanogenic bacteria and affecting the proportion of methanogenic bacteria.Under the screening effect of cefotaxime sodium,the total number of resistance genes and β-lactam resistance genes increased,the total number of β-lactam resistance genes decreased,and the proportion of β-lactam,multidrug and fluoroquinolone resistance genes increased.