Research On Cooperative Relationship Between Microbial Community And Quorum Sensing On Performance Of Activated Sludge

Exploring the messenger relationship of the coordination of quorum sensing and microbial community succession to system performance of activated sludge system is of great significance to deepen the understanding of the essential rules of system regulation and to provide important reference for enhanceing the ability and stability of the system.In this paper,the SBR reactors under different operating conditions(carbon sources,acetic acid/oleic acid ratios,sludge loads and fluctuating loads)and the operational wastewater treatment plants were investigated,and the regulatory relationship among system performance,quorum sensing and microbial community in the activated sludge system were analyzed.The main results are as follows:(1)Four carbon sources(sodium acetate,glucose,starch and Tween 80)had significant differences in nitrogen and phosphorus removal,sludge settleability and EPS contents of SBRs.Different regulatory correlations were observed in reactors fed with different carbon sources,among which AHLs mainly mediated the production of EPS,and different carbon sources had significant influence on microbial community.Canonical correspondence analysis revealed that the interaction between microbial community and quorum sensing affected the system performance.(2)COD,TN and PO₄^3--P removal and sludge settleability of the reactors were considerably affected by the acetic acid/oleic acid ratios.Research on quorum sensing regulation showed that the reason for the above differences was that AHLs-mediated quorum sensing played significant role in the COD and TN removal,sludge settleability,sludge particle size and the production of EPS.The correlation analysis between functional bacteria and system performance revealed the reason for the differences of system performance,and the correlation analysis between AHLs and bacteria genus revealed the reason for the regulation differences of quorum sensing.(3)Under different influent loads condition,the sludge settleability became worse and more EPS were produced with the increase of influent load.C10-HSL mainly mediated the removal of NH₄⁺-N under different load conditions,while C8-HSL,3OC12-HSL and 3OC14-HSL mainly regulated the PO₄^3--P removal.The different abundance of Thiothrix led to the difference of sludge settleablity in the reactors.Thiothrix,Ramlibacter,Sulfuritalea and Mesorhizobium were the main EPS producing bacteria,while Nitrospira,Sphingobium and Dokdonella were the main AHLs producing bacteria in the system.(4)The study on microbial community behavior under fluctuating load showed that the fluctuating load was easy to cause sludge bulking and produce more EPS.And more regulation behaviors based on quorum sensing were observed under the fluctuating load condition.Function prediction analysis showed that fluctuating load inhibited the activity of nitrate reductase and 3-hydroxybutyrate dehydrogenase,which reduced the nitrogen and phosphorus removal,and promoted the activity of amino sugar and nucleotide sugar metabolism and fatty acid biosynthesis,which resulted in more EPS production and more regulation behaviors based on quorum sensing.(5)The study on microbial community behavior of operational wastewater treatment plants showed that sludge bulking occurred in the investigated wastewater treatment plants during the winter and spring seasons.Microbial community studies have shown that Candidatus Microthrix and f?Anaerolineaceae?Unclassified were the genus responsible for the variation of sludge settleability.C6-HSL and 3OC12-HSL mainly regulated the sludge settleability,while 3OC8-HSL and 3OC12-HSL mainly regulated the production of EPS.The microbial community analysis showed Ferruginibacter,Terrimonas and metagenome might be the main EPS producing bacteria,while metagenome and Ellin6067 might be the main AHLs producing bacteria.