Characterization of extracellular polymer substances and acyl-homoserine lactones of sulfur-based autotrophic denitrification microbial community under high nitrate loading
Characterization of extracellular polymer substances and acyl-homoserine lactones of sulfur-based autotrophic denitrification microbial community under high nitrate loading
Sulfur-based autotrophic denitrification(SADN)was influenced by hydraulic retention time(HRT)and influent NO3--N concentration.By progressively shortening the HRT and increasing the influent NO3--N concentration,the nitrogen removal limit of the process was explored.Simultaneously,the changes in extracellular polymeric substances(EPS)and signal molecules acyl-homoserine lactones(AHLs)were analyzed,along with the evolution of microbial community structure in this process.During the transition from an HRT of 4.1h to 1.0h,SADN bacteria rapidly adapted to the environment.When the HRT was 1.0h and the influent NO3--N concentration was 40mg/L,the system achieved a TN removal rate of 99.74％,with a denitrification load as high as 958.53mg/(L·d).In this process,the increase in EPS concentration was mainly driven by TB-PN and TB-PS,while the increase in AHLs concentration was primarily led by C4-HSL.In comparison to shortening the HRT,raising the influent NO3--N concentration significantly increased the C4-HSL concentration,leading to a gradual trend towards an unstable state in the sludge structure.C6-HSL,the predominant AHL in the system,exhibited substantial growth in stages G4 and G7,reflecting a self-regulation by the microorganisms following the weakening of the system's denitrification capability.Analysis of the microbial community composition indicated that system operation and nitrogen load variations drove the domestication selection of microbial communities.In the reduced HRT group,norank_f_Pleomorphomonadaceae of Proteobacteria played a primary role as the dominant bacterial genus,providing substrates for denitrification bacteria to sustain system stability.Following the increase in NO3--N concentration,UKL 13-1,Simplicispira,Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium,and Thermomonas gradually evolved into dominant bacterial genera,all crucial microorganisms with denitrification capabilities.
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