Effects Of Quorum Sensing And Quenching On Aerobic Granular Sludge

Aerobic granular sludge(AGS)has been widely concerned for its characteristics of good sedimentation performance,strong impact resistance,abundant microorganisms and high efficiency of nitrogen and phosphorus removal.potential.However,AGS,as a special biofilm structure,processes a long period of formation and poor stability,which limits the application and development of this technology.Therefore,this article analyzes the process of aerobic granular sludge formation and expansion from the perspective of quorum sensing and quenching effects,discovers the changes of signal molecules and EPS components,explores the formation mechanism of AGS,and regulates the quorum sensing and quenching effects.The impact on AGS provides solutions for the rapid cultivation and stable operation of AGS.The conclusions are as follows:(1)During the formation of AGS,the particle size of sludge kept increasing,finally,the average particle size was about 150 ?m,which significantly improved the removal effect of pollutants and content of EPS,especially the relative protein of metabolic process and catalytic activity.During the granulation,Acyl-homoserine lactones(AHLs)content increased from 1858.2 mg/gMLVSS to 2583.3 mg/gMLVSS,which enhanced quorum sensing.Among them,C6-HSL and C8-HSL had obviously positive correlation with TB-PN,TB-PS and TB-EPS.During the granulation,42.53% of the functional proteins were concentrated in molecular functions,17.96% in cell components,and 39.52% in the biological process.Gemmobacter and Saccharibacteria increased significantly in AGS,Stenotrophomonas and Rhizobium which are related to quorum sensing and quenching also had a significant change during the granulation.(2)Along with the bulking of aerobic granular sludge,the structure of sludge became unstable,SVI and zeta were gradually increased.EPS content of AGS was also significantly increased,especially SMP-PN and TB-PN.The AHLs content increased from 1278.1 mg/gMLVSS to 4307.1 mg/gMLVSS,which enhanced quorum sensing and sludge bulking.During the bulking of aerobic granular sludge,41.98% of the functional proteins were concentrated in molecular functions,18.06% in cell components and 39.96% in the biological process.With the rapid growth of filamentous bacteria,the content of Sphaerotilus increased significantly.Quorum sensing was mainly supported by Nitrospira,Rhodobacter and Rhizobium,while quorum quenching was mainly supported by Flavobacterium and Acidovorax.(3)After the addition of AHLs in the initial AGS,the AHLs content increased from 2404.0 mg/gMLVSS to 3081.8 mg/gMLVSS,which enhanced quorum sensing and further accelerated the growth of biofilm and promoted the metabolism of microorganisms in aerobic granular sludge.Enhancing quorum sensing is beneficial to achieve a better denitrification effect and increase biodiversity.Chromatiales,Alphaproteobacteria and Prosthecobacter turned into the predominant bacteria.With the enhancement of quorum quenching in bulking AGS,the content of EPS only created a slight variation,but the settlement property was significantly improved.The bulking sludge system has better impact resistance.The microorganisms related to quorum sensing increased during the improvement process of quorum quenching,also the content of Acidovorax increased,and the content of Haliscomenobacter decreased,which effectively inhibit the proliferation of filamentous bacteria.