Control Of Antibiotic Resistance Contamination By Membrane Technology And Regulation Of Membrane Surface Biofilm

The extensive use of antibiotics has seriously polluted the ecological environment,especially the water environment.Municipal wastewater treatment plants(WWTPs)receive wastewater from hospitals,pharmaceutical factories,and aquaculture,resulting in the frequent detection of antibiotics in WWTPs.Under the long-term selection pressure of antibiotics,a large number of antibiotic resistant bacteria(ARB)and antibiotic resistance genes(ARGs)were generated in the sludge system.However,the traditional water treatment process can not effectively remove emerging organic contaminants such as antibiotics and ARGs,resulting in the widespread of bacterial antibiotic resistance in the water environment,which imposing potential threats on human health and public health securityMembrane separation technology can be used as an advanced treatment process for controlling the further transfer of antibiotics and ARGs in WWTPs to the receiving water.However,microfiltration and ultrafiltration have a limited removal efficiency to antibiotics and ARGs.Though nanofiltration and reverse osmosis processes can have excellent removal of these contaminants,the energy consumption are relatively high,and the quality of influent water are strict.Therefore,the development of novel loose nanofiltration membrane with high removal efficiency and low energy consumption is the key to remove antibiotics and resistance genes by membrane separation technology In addition,the formation of biofilm on the membrane surface is a bottleneck for the widespread application of membrane technology,which will reduce membrane flux,aggravate the proliferation of ARB,and accelate the horizontal transfer of ARGs on the membrane surface.Biofilm formation is closely related to quorum sensing.The quorum sensing inhibitor can hinder the occurrence of quorum sensing,regulate the formation of biofilm on the membrane surface,and then alleviate the biofouling on membrane surface.Based on the above research background,a loose nanofiltration membrane was developed for antibiotics and ARGs removal.Then,the biofilm formation was controlled by grafting quorum sensing inhibitors on membrane surface.The main research contents and conclusions of this study are as follows:1.Using the layer-by-layer(LbL)self-assembly technology,a loose nanofiltration membrane was developed on the surface of the polysulfone ultrafiltration membrane by the electrostatic interaction between the cationic polyelectrolyte,poly(diallyldim-ethyl ammonium chlorideand)and anion polyelectrolyte,poly(styrene sulfonate).The performance of LbL membranes with different polyelectrolyte double layers(1,2,3 layers)was evaluated for antibiotics and ARGs removal.Quantitative analysis of antibiotics and ARGs was performed using HPLC and real-time quantitative qPCR.The results showed that the presence of polyelectrolyte layer could effectively improve the removal efficiency of sulfamethoxazole,and as the number of polyelectrolyte layers increased,the removal efficiency improved.The removal of 16S rRNA was also enhanced with the increased number of polyelectrolyte layers.The removal efficiency of 16S rRNA by three polyelectrolyte double layers could reach 96%.When the polyelectrolyte double layer was increased from 1 to 2,the removal efficiency of the membrane on the sulfonamide resistance gene sul2 was improved,and further increase would not affect sul2 removal.The membranes with different layers of polyelectrolyte could effectively remove the chloramphenicol resistance gene floR,and the removal efficiency was above 99%.2.A kind of mussel bionic material polydopamine(PDA)was used as the intermediate layer,and two natural quorum sensing inhibitors vanillin and furanone were grafted on the membrane surface.The surface morphology and chemical bond changes of the membrane were characterized by SEM and FTIR.The water contact angle,porosity,pure water flux and other properties of the membrane before and after modification were evaluated and the antibacterial performance,biofilm regulation and antifouling performance were tested.The results showed that vanillin and furanone were successfully modified on the membrane surface without destroying the original membrane pore structure.The presence of PDA,vanillin and furanone improved the hydrophilicity and pure water flux of modified membranes.The porosity of the membranes didn't change too much.The vanillin modification could effectively inhibit the P.aeruginosa PAO1 biofilm formation on the membrane surface,and the inhibition ratio could reach 81.7%.Furanone modification can inhibit both E.coli MG1655 and P.aeruginosa PAO1 biofilm formation,the inhibition ratio were 42.5%and 49.6%,respectively.The membranes modification with the two inhibitors also showed reducing biofouling during the dynamic filtration process.