Study On The Diversity And Metabolic Potential Of Microbial Community Of Activated Sludge In A Mixed Urban Wastewater Treatment Plant

With the development of industrialization and urbanization,the discharge of industrial and urban wastewater increases obviously in China.China has built more than 4,000 wastewater treatment plants（WWTPs）.WWTPs in the Yangtze Delta are mainly mixed with 30%-70%of industrial wastewater,which leads to frequent changes in influent quality and quantity,unstable pollutants removal performance,and high effluent ecological risk.In this thesis,three biological units of typical mixed urban WWTP in the Yangtze Delta are selected to study the influent composition,microbial community,and metabolic potential by integrated meta-omics.The response mechanism of key metabolic potential of pollutants in mixed urban WWTPs under the stress of textile-dyeing industrial wastewater was analyzed.The main results are as follows:（1）Analysis of influent quality characteristics of different biochemical units in mixed urban WWTPs showed that the influent total nitrogen（TN）concentration of municipal wastewater was higher,and BOD₅/TN ratio was lower,which was40.09±6.24 mg/L,and 2.75±0.51,respectively.After mixing with textile-dyeing wastewater,the influent TN concentration was reduced to 28.29±5.32 mg/L,and BOD₅/TN ratio was increased to 4.26±0.88,but the removal efficiency of TN concentration was only 70.6±6.6%,indicating that the denitrification efficiency was inhibited.Combined with the analysis of liquid chromatography-high resolution mass spectrometry,it was found that the biotoxic butylated hydroxytoluene（BHT）was the characteristic pollutant of the mixed urban WWTP with the concentration of 0.447mg/L.It was inferred that BHT could inhibit the activity of denitrifying bacteria,which was the main reason for the poor denitrification efficiency of the mixed urban WWTP.（2）The microbial diversity of activated sludge in mixed wastewater system was lower than that in municipal wastewater system significantly（p<0.05）.LEFSE was used to analyze the significantly different species.Nitrososphaeria,Hyphomicrobium,Methylophilaceae,and functional microbes were the dominant microbes in mixed wastewater system.RDA analysis further confirmed that the dominant microflora was significantly correlated with BHT（p=0.002）.Among them,Hyphomicrobium was a phenolic resistant genus and core organisms（LDA>4）.The results showed that under the stress of textile-dyeing wastewater,and the microbial diversity was decreased,while the denitrifying functional microbes were still the dominant microbes.（3）Compared with the municipal wastewater system,the abundance of functional genes related to denitrification and nitrogen respiration significantly decreased in the mixed wastewater system（p<0.01,T test）.Metabonomics analysis showed that the contents of cis-Aconitate,α-ketoglutarate,Glutamate,2-keto-D-Gluconic acid,and alpha-D-Glucose-6-phosphate significantly decreased（log₂FC<-1,p<0.05）.The pathway enrichment analysis of the above metabolites showed that the metabolism of amino acids,purine and pyrimidine,glycerol phospholipids and other basic anabolism pathways were inhibited,and the carbon metabolism,such as pentose phosphate and TCA cycle,were significantly inhibited（p<0.05,R>0.6）.In summary,the abundance of denitrifying microbe was relatively high in the mixed wastewater system under influent stress,but the abundance of denitrifying genes increased and carbon metabolism was significantly inhibited,as a result that the removal efficiency of TN in the mixed system was low.This study can provide a theoretical basis for improving the water quality and treatment efficiency,and enhancing the growth of functional microbes in mixed urban WWTP.