Potential biomethane productivity in the temperature phased anaerobic digestion process: Impact of organic load rate and solid retention time of acidogenic phase

Abstract

This study evaluated the biochemical methanogenic potential (BMP) of effluents from a thermophilic acidogenic anaerobic membrane bioreactor (AMBR) operated semi-continuously at different hydraulic retention times (HRT) and solids retention times (SRT). Thus, the influence of organic loading rate (OLR) and sludge age on mesophilic methane production was evaluated. In addition, two kinetic models (Gompertz and Cone) were proposed as tools for modelling methane production. An 18.7 % increase in OLR (from 4.48 to 5.32 gVS/L·d) in the acidogenic reactor results in a 9.4 % increase in effluent biodegradability, which enhances the methanogenic phase and increases methane production by 23.9 % in volume (from 271.05 to 335.84 mL CH4) and 42.8 % in yield (from 127.85 to 182.52 mL CH4/gVSadded). For an OLR of 4.48 gVS/L·d, extending the SRT from 6 to 12 days results in a 20.9 % increase in methane production volume (from 271.05 to 327.65 mL CH4) and a 14.9 % increase in yield (from 127.85 to 146.93 mL CH4/gVSadded). For an OLR of 5.32 gVS/L·d, extending the SRT from 4 to 8 days results in improved total solids (TS) and volatile solids (VS) removal, as well as a 20.9 % increase in methane production by volume (from 335.84 to 406.12 mL CH4). In both scenarios, extending the SRT leads to a longer lag time (λ) for methane production, with the Gompertz model fitting better than the Cone model.