Semi-continuous anaerobic digestion of the organic fraction of municipal solid waste: digester performance and microbial population dynamics

Abstract

Anaerobic digestion is an attractive approach for the management of organic fraction of municipal solid waste (OFMSW) and for the recovery of energy from this waste. A semi-continuous digestion of OFMSW was conducted on stirred reactor under mesophilic condition. Three organic loading rates (OLRs) were tested throughout the anaerobic process (1.36, 2.5 and 3.5 g VS/L.d). The achieved results showed that biogas yield decreased with the increase of OLR. Thus, the highest average of biogas yield, 0.51 L/g VS, was recorded at low OLR (OLR1:1.36 gVS/L.d). Likewise, optimal VS removal, pH, VFA and alkalinity were obtained at OLR1 compared to the other tested OLR. During the anaerobic digestion, the dynamic of microbial community was also assessed by the high-throughput sequencing technology. Firmicutes, Bacteroidetes and Proteobacteria were the dominant phyla during the digestion process. This could be related to their roles in hydrolysis of different OFMSW compounds, as well as in acidogenesis and acetogenesis steps. Regarding Archaeal population, the relative abundance of the Methanoculleus genus declined, while Methanosarcina increased over time. This indicated that acetotrophic and hydrogenotrophic pathways were used for methane production.