Research On Enhanced Removal Mechanism Of Microbial Algae Symbiotic MBR Pollutants And Membrane Pollution Control Based On Microbial Population Sensing

Traditional MBR has issues such as the need for further improvement in nitrogen and phosphorus pollutant removal efficiency and difficulty in controlling membrane pollution.Microalgae are widely present in natural water bodies.Currently,research on bacterial algal symbiotic reactors is also relatively in-depth.Therefore,this study uses a bacterial algal symbiotic reactor to not only alleviate the problem of poor nitrogen and phosphorus removal efficiency in traditional MBR,but also improve the recovery rate of microalgae through membrane separation,This also echoes the dual carbon plan advocated by the current country.In addition,another obstacle to the promotion and application of MBR is membrane fouling,with irreversible fouling being the most severe.A series of studies have shown that membrane fouling is closely related to microbial quorum sensing.When the signal molecules generated during microbial growth reach a certain concentration,they will regulate a series of cellular behaviors,such as biofilm formation and luminescence But at present,the research on quorum sensing effect mainly focuses on the intercellular and intracellular of bacteria,while the research on the response of eukaryotic cell to bacterial signal molecules is less.In this study,the relationship between nitrogen and phosphorus nutrient removal,membrane pollution and bacterial quorum sensing in MBR reactor was explored,which has important scientific and theoretical significance and technical application value.By studying the wastewater treatment efficiency,quorum sensing,and membrane fouling mechanisms of traditional MBR,it was found that the concentration of six bacterial signaling molecules showed an increasing trend with the prolongation of reactor operation time,with C6-HSL,C8-HSL,C10-HSL,and C12-HSL being the main ones.On this basis,the role of signal molecules in the extracellular polymer and aggregation characteristics of microalgae was further explored.Different types of bacterial signal molecules were injected into the same type,concentration,and content of algal solution to observe and analyze the aggregation characteristics of algal solution,the removal effect of nitrogen and phosphorus,and the changes in extracellular polymer and Zeta potential.The increase in polysaccharide content in TB-EPS was the largest,increasing from 1±0.5 mg/g MLSS to 3.5±0.5 mg/g MLSS.The protein content in SMP,LB-EPS,and TB-EPS increased from the initial 3.5±0.5mg/g MLSS to 4.5±0.5 mg/g MLSS,4.5±0.5 mg/g MLSS,and 5.5±0.5 mg/g MLSS.Parallel operation of traditional membrane bioreactor(C-MBR)and bacterial algal symbiotic membrane bioreactor(ASB-MBR)was conducted to compare the pollutant removal efficiency,changes in extracellular polymer and signal molecule concentrations during the operation of the two reactors.The correlation between extracellular polymer concentration and nutrient removal was explored,and the mechanism of nitrogen and phosphorus nutrient enhanced removal was analyzed to assess the inner membrane pollution of the reactor.Compared to C-MBR,ASB-MBR has better nitrogen and phosphorus removal efficiency.The ammonia nitrogen removal rate of ASB-MBR is about 2% higher than that of C-MBR,and the total nitrogen and phosphorus removal rate is about 10% higher.The five signaling molecules C6-HSL,C8-HSL,C10-HSL,C12-HSL,and 3-oxo-C12-HSL in ASBMBR play a major role in membrane fouling.Among them,C6-HSL,C8-HSL,and 3-oxoC12-HSL do not have a dominant effect on membrane fouling in the later stage,but have a relatively greater impact on microalgae aggregation.C10-HSL and 3-oxo-C12-HSL maintain sustained growth and play a major role in the later stage of membrane fouling.In addition,the average protein content in the extracellular polymer of ASB-MBR increased,with an average protein concentration of about 10.7%.However,the polysaccharide concentration showed a decreasing trend compared to C-MBR,with a decrease of about 22%.And there is a good correlation between the concentration of extracellular polymers in ASB-MBR and the removal rate of nitrogen and phosphorus.The concentration of ammonia nitrogen and total nitrogen in TB-EPS of ASB-MBR extracellular polymer showed a significant increase compared to C-MBR,with an average increase of about 10%.The concentration of ammonia nitrogen in cells was also slightly higher,and the concentrations of SMP,TB-EPS,and total phosphorus in cells were also increased to a certain extent compared to C-MBR.The increase in SMP,TB-EPS was about 10%,and the increase in cells was about 25%,indicating that bacterial and algal extracellular polymer can adsorb excessive nitrogen and phosphorus elements in water into the extracellular polymer for storage,and then transported to intracellular assimilation and utilization.Through changes in TMP,it was found that the symbiotic system of bacteria and algae contributes to the alleviation of membrane pollution.The time for TMP to reach the same value of 12 KPa in ASB-MBR was delayed by about 5days,and the alleviation mainly occurred in the later stage of stable development of membrane pollution and the hydraulic change period of the pollution layer.Further analysis was conducted on the impact of the symbiotic system of bacteria and algae on the reactor treatment efficiency and membrane fouling,focusing on the changes in membrane fouling.Through analysis and research on membrane surface pollution,it was found that the mud cake layer formed on the surface of ASB-MBR contaminated membrane has a porous structure,which is an important reason for slowing down the membrane pollution process.In addition,from the changes in the microbial community structure of the two reactors,compared to C-MBR,ASB-MBR has relatively lower biodiversity,reduced complexity of bacterial community structure,and significant differences in species between the two systems.The three phyla with the highest proportion in C-MBR are Proteobacteria,Bacteroidota,and Firmicutes.The three bacteria that account for the largest proportion in the ASB-MBR are Proteobacteria,Bacteroidota and Myxococota.The dominant bacteria have changed.The relative abundance ratio of Proteobacteria bacteria in the ASB-MBR system is64.76%,4.51% higher than that in the C-MBR system.Bacteroidetes bacteria have also been enriched to a certain extent in the ASB-MBR system,with a relative abundance ratio increased by 1.64%,while the relative abundance ratio of Firmicutes bacteria has decreased.Firmicutes bacteria are a type of bacteria that easily adhere to the membrane surface and can easily aggravate membrane fouling.This indicates that changes in microbial community structure affect the concentration of signaling molecules and extracellular polymers within the system,thereby affecting membrane fouling.This study aims to investigate the influence of bacterial quorum sensing effect on the expression of extracellular polymers in microalgae in the symbiotic MBR of bacteria and algae,to form a nutrient enhanced removal technology,and effectively control the formation of membrane pollution.This will have important scientific theoretical significance and technical application value.