Research On The Effect Of Metal Ions On The Microbial Community In Membrane Bioreactor

Membrane bioreactor is a new type of reactor for water treatment with a organic combination of the traditional precipitation and filtration membrane technology.As a new and efficient sewage treatment and water reuse technology,it draws people's at-tention.The membrane fouling is always the bottleneck of membrane bioreactor ap-plication.Studies have shown that different valence and concentration of metal ions have different effects on membrane fouling.Existing research is basically through monitoring the membrane fouling-related microbial extracellular polymeric substanc-es(EPS),soluble microbial products(SMP)physicochemical to analyze the nature of the metal ion effects on membrane fouling processes and mechanisms.There are many controversial findings.The trial starting from the microbiological point of view of ecology.Environmental microbiology analysis will be based on a new generation of high-throughput sequencing(Illumina sequencing technology)and analyzeing togeth-er with EPS and SMP composition and content,the film surface morphology and the water quality.We studied different valence and concentration of metal ions(Na+,Ca2+,Mg2+,Fe3+,Al3+)effects on microbial community structure consistling of MBR and elaborated metal ions affect the structure and physical characteristics of microbial communities to change the content of microbial metabolites and microbial ecology mechanism of membrane fouling processes.The main conclusions are as follows:(1)Adding a monovalent metal(Na+)to membrane bioreactor during operation,and Na+ is to speed up the rate of membrane fouling.Correlation analysis of Integrat-ed environmental factors and microbial ecology evolution display and there is a sig-nificant correlation between membrane fouling and microbial community structure.Salinity will affect community composition of sludge,making microbial community diversity decline,and community structure and diversity of different salinities MBR samples are not the same.At the genus level,the case of some high-salt increases with the increasing salinity.These properties may be adjusted carbohydrate metabolism osmotic pressure to overcome the impact of salt.EPS(PS)and SMP(PS)are such proportion as resistant to high salt concentrations.Polysaccharide concentration in-creasing exacerbated membrane fouling.(2)The addition of divalent metal(Ca2+,Mg2+)in membrane bioreactor during operation slowed down the membrane fouling.But the integrated environmental fac-tors and microbial community structure analysis,did not find the microbial commu-nity structure and membrane fouling relevance.This means that Ca2+,Mg2+ mainly through the bridging role of divalent cations,increasing the activated sludge floccula-tion,thereby slowing the rate of formation of the filter cake from the physico-chemical process,and ultimately affect the membrane fouling rate.(3)Adding a trivalent metal,namely,hydrolysis of metal(Fe3+,Al3+)to membrane bioreactor during operation effectively reducing the membrane fouling processes.Fe3+ was more obvious compared the effect of Al3+.Considering the changes in the environment factors and the microbial community structure,it showed significant correlation between the presence of membrane fouling rate of evolution of microbial communities.From phylum and genus level analysis,we could find Fe3+,Al3+ leads to an increase or reduce in the proportion of certain microorganisms.So,on membrane fouling mitigation,Fe3+,Al3+ not only enhances coagulation and slow down cake formation rate,but also changed the overall metabolism of microbial communities.The concentration of EPS and SMP changes,and ultimately affect the membrane fouling processes.In summary5the analysis combines the results of sludge microbial community structure,water quality,EPS and SMP,the composition and content of sludge char-acteristics and the membrane fouling rate.The results showed that monovalent met-al(Na+)have an impact on the community structure,and is associated withmembrane fouling.The divalent metal(Ca2+,Mg2+)can affect the microbial,but there is no sig-nificant correlation with membrane fouling.Hydrolysis of metal(Fe3+,Al3+)can affect the sludge flocculation,and the influence on the biological communities and mem-(brane fouling were significantly related.Environmental microbiology analysis is to-gether with EPS and SMP composition and content,the film surface morphology and the water quality.We studied different valence and concentration of metal ions effects on microbial community structure consisting of MBR and elaborated metal ions affect the structure and physical characteristics of microbial communities to change the content of microbial metabolites and microbial ecology mechanism of membrane fouling processes.We aim to provide a scientific basis for the high salt MBR wastewater treatment and inorganic coagulant added strategy of MBR membrane fouling process.