Effect Of Quorum Quenching On Membrane Biofouling Of MBR At Different Aeration Intensities

Membrane bioreactor(MBR),a new-type technology that conventional activated sludge method was combined with membrane separation technique for water treatment.Due to the unique advantages in effluent quality,organic loading of feed water and reactor footprint,MBR was developing into the most promising technique for wastewater treatment and reuse.However,membrane fouling of MBR,especially biofouling,was the biggest obstacle which limited its development.Biofouling was a process attributed to the biofilm formation on membrane surface,which decreased the membrane flux significantly.It was reported that the biofilm formation was closely related to quorum sensing(QS)process of microbial.Therefore,inhibiting the QS process through quorum quenching(QQ)was a valid way to control biofilm formation and membrane biofouling effectively.Cell entrapped beads(CEBs)that embedded with QQ bacteria was used as the QQ-media in this study,and the effect of QQ on membrane biofouling control at different aeration intensities was investigated.By monitoring the transmembrane pressure(TMP)and EPS content of biofilm in MBR continuously,we found the rising trend of TMP in QQ-MBR(with CEBs)was obviously lower than C-MBR(with vacant beads),and the EPS content of biofilm was reduced by QQ effect at the same time.The result confirmed that QQ was able to mitigate membrane biofouling efficiently.At low or high aeration intensities(1 L/min or 2 L/min of air flow rate),the result indicated that microbial activity was low and the QQ performance was unstable at low aeration intensity(LA).However,the microbial activity was high and the biodegradation capacity of organics was improved at high aeration intensity(HA).Besides,the investigation found that the QQ effect on EPS characteristic was focus on TB-EPS(tightly bound EPS)and the reduction was 90 mg/L.The influences of QQ on SMP(soluble microbial product)and LB-EPS(loosely bound EPS)were negligible.The reduction of polysaccharides and proteins were 20% and 15% separately.At different aeration intensities,the sludge characteristics and membrane biofouling of QQ-MBR and C-MBR had the different result.With the reduced EPS content in QQ-MBR at HA,the settleability and stability of sludge flocs were greater.The relatively hydrophobicity and fouling propensity of sludge was decreased.However,due to the unstable QQ performance,the QQ effect on sludge properties was only happened in sludge hydrophobicity.The QQ-MBR at LA had the similar rising trend of TMP as C-MBR at HA and it was attributed to the improved scouring effect of vacant beads on membrane surface.Owing to the synthetic effect of CEBs,the QQ-MBR at HA had the slowest fouling rate.A measurement on CEBs activity was made after their application and the result indicated that the CEBs used at LA was completely inactive,while the CEBs still had great QQ activity at HA.Moreover,to investigate the influence of organics content of mixed liquor on QQ activity,we found that the difference of EPS concentration between two MBRs needed sufficient organics to maintain.The QQ process was achieved by regulating the proteins concentration in mixed liquor.