Microbial Communities and Sludge Specific Resistance in Two SBRs Treating Leachate

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The relationship between microbial populations and sludge filtration performance was studied when active sludge was used to treat the leachate from municipal solid waste incineration plants. Two SBRs (SBR1 and SBR2) were operated at the same conditions, except that SBR1 was exposed to the sunlight and SBR2 was in the dark. To identify the difference in microbial populations in two reactors, high-throughput sequencing method was used. On the 50th day, the fungi abundance in SBR2 was higher than in SBR1. Phylum Rozellomycota became the dominant fungi in SBR1, whose relative abundance was 83.71%. Phylum Basidiomycota and Genus Trichosporon became only dominant fungi in SBR2, whose relative abundances were 99.84% and 99.78%, respectively. Bacterial abundance in SBR1 was higher than in SBR2. In SBR1, Thauera was the major bacterial genus, whose relative abundance was 39.35%. In SBR2, Planktosalinus, Thauera, and Ottowia were the major bacterial genera, whose relative abundances were 16.84%, 16.23%, and 12.55%. Rotifers and other predatory metazoan were detected on the 30th-50th days in SBR1 and sludge specific resistance began to decline on the 35th day. Filamentous fungi bulking caused by Trichosporon resulted in a continuous increase in sludge specific resistance of SBR2. The dominant microbial communities (especially fungi) and sludge specific resistances in SBR1 and SBR2 were very different because of the effect of sunlight. Therefore, sunlight plays an important role on microbial communities and sludge characteristics.