Succession from acetoclastic to hydrogenotrophic microbial community during sewage sludge anaerobic digestion for bioenergy production

Abstract

To evaluate microbial profiling during the anaerobic digestion (AD) of sewage sludge (SWS) from a municipal Wastewater Treatment Plant (WWTP), a Biochemical Methane Potential (BMP) assay operating at 37°C mono-digestion was performed. The results from 16S ribosomal RNA (rRNA) gene sequencing, utilizing the Illumina MiSeq platform, revealed a core bacterial community in the solid material, dominated by variations in the profiles. The relative abundance in the SWS (before AD) was as following: Proteobacteria > Bacteroidota > Actinobacteriota. After AD, the relative abundance shifted to Firmicutes > Synergistota > Proteobacteria. At the genus level, Sporanaerobacter and Clostridium were dominant. The methanogenic community presented a shift in metabolic pathway from acetoclastic to hydrogenotrophic in the lab-scale reactors. The dominance of methanogenic groups at the genus level was represented by Methanosaeta > Methanolinea > Methanofastidiosum. After AD, the dominance shifted to Methanobacterium > Methanosaeta > Methanospirillum. This shift in the metabolic pathway could be related to the increase in Firmicutes, especially the population of Clostridia, which contains acetate-oxidizing bacteria that convert acetate to hydrogen.