The Mechanism Exploration Of Antibiotic Degradation And Enhanced Removal In Membrane Bioreactor

The extensive use of antibiotics has seriously polluted the environmental ecosystem,especially the water environment.And Antibiotic accumulation in water,the resulting selective pressure,has made the environment Antibiotic resistance bacteria(ARB)and resistance genes(ARGs),a lot of antibiotic resistance genes,Bring potential safety hazards to the water environment ecosystem.Antibiotics can be biodegraded in ecosystems under aerobic and anaerobic conditions by metabolic and co-metabolic means,but the relationship between microbial communities and antibiotic degradation remains unclear.The removal efficiency of most antibiotics in traditional sewage treatment plants is low,but it can be basically removed under laboratory conditions,which may be caused by the difference in antibiotic concentration.Therefore,this study examined the degradation pathway of typical antibiotic Sulfamethoxazole(SMX)under the low concentration gradient of Membrane Bio-Reactor(MBR),and explored the degradation mechanism during the degradation process.The degradation of SMX was controlled by increasing the initial dosage of low concentration antibiotics and adding signal molecules.The main conclusions of this paper include:(1)In the gradient dosing process,the degradation pathway was difficult to be activated by the initial dosing of 0.05 mg/L SMX and could not be degraded until the dosing concentration reached 0.5 mg/L.When the initial dosage of 0.2 mg /L and 0.5mg /L SMX were increased,the degradation of SMX was achieved in a relatively short time,and the removal rate of SMX was faster with the increase of the initial dosage concentration.The comparison showed that when the initial dose of SMX was 0.05mg/L,the antibiotic concentration required to activate the degradation pathway would be higher and the time would be longer.Swarm sensing effect is a gene regulation mechanism evolved by bacteria to adapt to the changing environment.Bacteria regulate the expression of related genes by releasing signal molecules,and the addition of foreign signal molecules will activate the degradation pathway and promote the degradation of SMX.And when the degradation pathway is activated,the limit of low concentrations that are hard to degrade can be broken.(2)The results of batch experiments showed that aerobic heterotrophic bacteria played a major role in SMX degradation in membrane bioreactor,rather than the role of nitrification co-metabolism.The degradation mechanisms in different reactors are consistent,and the core microorganisms in different reactor degradation stages have a high degree of similarity,which suggests that the degradation pathway of SMX in aerobic MBR is the same.Metagenomic results indicated that functional genes and resistance genes play important roles in activating SMX degradation pathways.During the degradation process,the abundance of the sul1 resistance gene increased by an order of magnitude in the degradation stage,and the abundance of conserved flavin monooxygenase cluster genes in all the sulfonamide-degrading bacteria was significantly up-regulated during the degradation stage.These findings provide fundamental support for the underlying mechanism and the proliferation of ARGs treatment and ARGs control.In this paper,the degradation mechanism and the action mechanism of degradation genes in the degradation stage of antibiotics were revealed by adding different initial SMX concentrations in the degradation process,which provided useful guidance for the treatment of antibiotic wastewater and the control of ARGs.