Effects Of Rhodococcus Sp. BH4 On Membrane Fouling In MBR At Different Aeration Intensities And Its Analysis Of Energy Consumption

Membrane bioreactor(MBR),as a novel and efficient wastewater treatment technique,has the advantages of compact footprint,high effluent quality,high organic and sludge loadings,as well as low production of excess sludge.At present,it has been considered as one of the most promising biotechnologies in the field of wastewater treatment.However,the problem of membrane fouling,especially biofouling,has been the main bottleneck limiting the promotion and development of MBR.It promotes the transmembrane pressure(TMP)to rise sharply,and enables the effluent to be destabilized seriously during the operation of MBR,thereby increasing the costs of operation and maintenance greatly.Quorum sensing(QS)is regarded as the direct cause for biofouling in MBR.It allows bacteria to communicate each other by the density-dependence,and express their genes,such as forming biofilm,etc.Yet,quorum quenching(QQ)can interfere with the bacterial QS behavior and inhibit biofilm formation,and thereby mitigate membrane fouling.Recently,QQ technology has been proven to be an efficient approach to control membrane fouling.It can improve sludge conditions,and reduce membrane pollutants content in MBR.Also,as one of the main operating parameters in MBR,aeration intensity is directly interconnected with membrane fouling.In this paper,Rhodococcus sp. BH4,the most typical indigenous QQ bacteria in MBR,was used as an immobilized strain and entrapped in sodium alginate beads,then was applied in MBR.We investigated the effects of BH4 on membrane fouling at different aeration intensities,and analyzed the various energy consumptions of MBR.Two reactors(control MBR/QQ MBR)were operated at three different aeration intensities: low(800 m L/min),middle(1600 m L/min)and high(2400 m L/min)aeration intensities,respectively.The monitoring results for the operation effect of two reactors showed that the addition of BH4 mitigated membrane fouling effectively,but the mitigation efficiencies were diverse at different aeration intensities.Both changing aeration intensity and add ing BH4 had little adverse influence on the pollutant removal capability of MBR.However,it may affect some characteristics of sludge,such as sludge volume index(SVI),zeta potential and relative hydrophobicity(RH),etc.,which changed the settlement,stability and membrane fouling propensity of sludge,and impacted the process of membrane fouling finally.Moreover,BH4 reduced the content of bacterial secreted substances in mixed liquor,biofilm and effluent of MBR,like SMP and EPS,etc.,thereby inhibiting biofilm formation,as well as the internal pore fouling of membrane module.It further confirmed the biofouling control effect of BH4.We observed that there were differences in the content and changing trend of these two substances in two reactors at different aeration intensities.BH4 exhibited the best reduction effect for SMP and EPS at middle aeration intensity,that is,too low or high aeration intensities may decrease the QQ performance of BH4 to some extent.The analysis for the energy consumption of MBR indicated that aeration intensity and addition of BH4 were closely related to the energy consumption of MBR.BH4 could decrease the specific energy consumption for membrane filtration to some extent,and the energy demands for aeration account ed for the highest energy consumption in MBR operations,which of specific value was positively correlated with aeration intensity.Also,we found that too high aeration intensity consumed a great energy,and BH4 could minimize the aeration intensity requi red for stable operation of MBR,thereby decreasing the total energy consumption of MBR.This study thoroughly analyzed the comprehensive effects of aeration intensity and Rhodococcus sp. BH4 on membrane fouling in MBR,then explored the effects of aeration intensity and BH4 on the energy consumption of MBR and its law of energy consumption proportion.Finally,the study revealed the potential effect of BH4(QQ technology)for decreasing MBR energy consumption.These findings provided new insights for the further development of QQ strategies and the energy savings of MBR.