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Methanogenic community structure in simultaneous methanogenesis and denitrification granular sludge

Sun, Yujiao, Zhao, Juanjuan, Chen, Lili, Liu, Yueqiao, Zuo, Jiane
Frontiers of environmental science & engineering 2018 v.12 no.4 pp. 10
Methanobacteriaceae, Methanosaetaceae, community structure, denitrification, granules, methane production, methanogens, molecular cloning, nitrates, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, sludge, upflow anaerobic sludge blanket reactor, wastewater
A laboratory scale up-flow anaerobic sludge bed (UASB) bioreactor fed with synthetic wastewater was operated with simultaneous methanogenesis and denitrification (SMD) granules for 235 days with a gradient decrease of C/N. Molecular cloning, qRT-PCR and T-RFLP were applied to study the methanogenic community structures in SMD granules and their changes in response to changing influent C/N. The results indicate that when C/N was 20:1, the methane production rate was fastest, and Methanosaetaceae and Methanobacteriaceae were the primary methanogens within the Archaea. The richness and evenness of methanogenic bacteria was best with the highest T-RFLP diversity index of 1.627 in the six granular sludge samples. When C/N was reduced from 20:1 to 5:1, the methanogenic activity of SMD granules decreased gradually, and the relative quantities of methanogens decreased from 36.5% to 10.9%. The abundance of Methanosaetaceae in Archaea increased from 64.5% to 84.2%, while that of Methanobacteriaceae decreased from 18.6% to 11.8%, and the richness and evenness of methanogens decreased along with the T-RFLP diversity index to 1.155, suggesting that the community structure reflected the succession to an unstable condition represented by high nitrate concentrations.