| With the continuous development of petrochemical,dye printing,pharmaceutical and iron and steel metallurgy and other industries,the discharge of industrial wastewater,especially phenol-containing wastewater,has increased significantly,and the resulting water environmental pollution problem has been widely concerned by researchers at home and abroad.Membrane-Bioreactor(MBR)is widely used in the field of wastewater treatment as an emerging and efficient water treatment technology,but the problem of membrane pollution caused by refractory phenolic compounds during operation has always limited its rapid development and wide application.In recent years,the electric field attached MBR(EMBR)has significant advantages in improving the efficiency of wastewater treatment and slowing down membrane pollution,and the magnetic powder has a broad application prospect in wastewater treatment due to its characteristics of magnetic biotic effect,adsorption capacity and electron transfer ability.However,at this stage,there are few studies on the efficiency of the magnetic powder-EMBR coupling system in treating phenol wastewater.Therefore,this study developed a new magnetic particle EMBR coupling system,systematically investigated the efficiency of the coupling system in the treatment of phenol wastewater and membrane pollution,and revealed the mechanism of improving the efficiency of phenol wastewater treatment and reducing membrane pollution by using microbial diversity analysis and metagenome sequencing technology.The degradation rates of phenol and COD,the activities of key phenol enzymes and the content of ATP in each system were detected to explore the efficiency of each system in treating phenol wastewater.The results showed that the degradation efficiency of phenol and COD in G4 system was higher than G2 system(EMBR system)> G3 system(MBR system)> G1 system(traditional MBR system),which was mainly attributed to the increase of key enzyme activities and ATP content.Microbial diversity analysis and metagenomic sequencing technology were used to investigate the changes in the structure and functional genes of microbial communities in the mixtures of each system,and the results showed that the application of appropriate electric fields and the addition of magnetic powders could enrich the dominant bacteria with the function of degrading phenol,while the coupling synergy effect of the electric field and the magnetic powder further enriched the dominant bacteria that degraded phenol.In addition,compared with G1,G3 and G2 systems,the expression of functional genes related to phenol degradation and electron transfer in G4 system was significantly up-regulated,and the expression of functional genes related to EPS synthesis was significantly down regulated,so as to improve the efficiency of phenol wastewater treatment and slow down membrane pollution.By determining the characteristics of activated sludge in the mixture of each system,the change of dissolved microbial metabolite(SMP),the absolute value of Zeta potential,and the content of extracellular polymer(EPS),the mechanism of slowing down membrane pollution in the magnetic powder-EMBR coupling system was revealed.The results show that the average growth rate of TMP in G4 system is significantly lower than that in G2,G3 and G1 system,effectively reducing the membrane fouling period,and the absolute value of Zeta potential in G4 system is significantly higher than that in G2,G3 and G1 system,enhancing the electrostatic repulsion between membrane pollutants and cathode film.Meanwhile,compared with G1 system,the contents of SMP and EPS in G4 system were significantly lower than those in G2 and G3 system.FTIR analysis showed that the vibration contraction intensity of absorption peaks of protein and polysaccharide functional groups in G4 system EPS was weaker than that in G2,G3 and G1 system.In addition,the dynamic changes of microbial community on the membrane surface were analyzed by microbial diversity.The results showed that the application of appropriate electric field and magnetic particle could reduce the relative abundance of dominant bacteria involved in biofilm formation,and the coupling synergistic effect of electric field and magnetic particle could further reduce its relative abundance. |
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