The Construction Of QQ-PAC Core-shell Structure Bead And Its Potential For MBR Membrane Fouling Control

Membrane bioreactor technology,combining with biodegradation process and membrane filtration process,has the advantages of efficient and reliable treatment effect,high biomass concentration and no sludge settling problems.Hence,it is widely used in sewage treatment and wastewater reuse,especially in retrofitting and upgrading water treatment systems for its small footprint.However,Membrane fouling is a bottleneck in the development and application of MBR,which requires additional energy consumption and manpower to maintain operation.In recent years,quorum quenching(QQ)based on microbial quorum sensing(QS)as a novel type of biological strategy to control membrane biofouling has achieved good effects.QQ can hinder the communication between cells by interfering with the communication mechanism of QS to inhibit the formation of biofilms,thereby delaying the process of MBR membrane biofouling.QQ bacteria can produce QQ enzymes to destroy signal molecules.It is the most researched and applied way of QQ strategy for MBR membrane biofouling control.In order to enable QQ bacteria to interfere with QS continuously,effectively,and economically,its immobilized technology arouses widespread concern.This study proposed the QQ core-shell structure bead possessing double-layer gel,with QQ bacteria as the inner core for quorum quenching and powdered activated carbon as the outer shell for adsorption and protection,to promote the synergistic effect of QQ bacteria and PAC for delaying membrane fouling.It was expected to provide a new research idea for subsequent scholars engaged in QQ Strategy.The microstructure of the bead was observed by scanning electron microscopy.The functional groups were revealed by Fourier transform infrared spectroscopy.Meanwhile,the mechanical strength,swelling property,penetration property and QQ activity of the core bead,the core shell-without PAC and the core shell-with PAC bead were compared.Finally,the function of the immobilized beads in MBR membrane fouling control was investigated.Observed by SEM,the surface morphology of the porous shell layer was rough and uneven,and the core part was a sponge mesh structure.The infrared spectrogram showed that the functional groups of the beads were mainly-COOH and-OH.The core-shell structure could wear through external shell layer to protect the internal core part with QQ bacteria and inhibit the swelling degree of alginate gel by water absorption.The addition of powdered activated carbon into the shell could improve the mass transfer conditions and its adsorption capacity,which was conducive to QQ effect of QQ bacteria entrapped in the core.Therefore,QQ-PAC core-shell beads could not only play an important role in quorum quenching by QQ bacteria,but also enhance physical washing effect and adsorption capacity of immobilized carrier materials.The QQ-PAC core-shell structure beads showed obvious membrane biofouling control in the MBR membrane fouling experiment by means of decreasing extracellular polymers(EPS)and membrane total adsorption biofilm(TAB).The operating period of MBR membrane module was 2.3 times that of the control group.