ANAEROBIC CO-DIGESTION OF WASTEWATER RESIDUALS WITH FOOD WASTE AND FOG: EFFECTS ON DIGESTER PERFORMANCE AND MICROBIAL COMMUNITY STRUCTURE

摘要

This study explored the anaerobic co-digestibility of waste activated sludge (WAS) with food waste (FW) and fats, oils and grease (FOG) at incremental co-substrate ratios of 25%, 50% and 75% (volatile solids basis) under step load and shock load conditions using semi-continuous lab-scale bioreactors at mesophilic conditions. In all, five experimental phases were explored and the microbial communities participating within the different phases were examined through 16s rRNA gene sequencing. From the co-digestion study, increasing FW fraction increased methane yield with 75% FW at 2 gVS/L/d, producing the highest average methane yield of 372.8 ±18 mL CH_4/g VS. Meanwhile, co-digestion with FOG was feasible only up to 50% FOG (vs basis), and inhibition occurred at 75% FOG. The bacterial community was dominated by Firmicutes during inhibitory conditions, whereas Bacteroidetes and Proteobacteria were mostly abundant during stable conditions. Hydrogenotrophic methanogens, particularly Methanolinea, dominated the archaeal community in all reactors, however, their abundance diminished during inhibitory conditions.