Long-term evaluation of methane production in a bio-electrochemical anaerobic digestion reactor according to the organic loading rate

Abstract

In this study, the effects of differing organic loading rates (OLRs) on methane production were evaluated via long-term operation of a bio-electrochemical anaerobic digestion (BEAD) reactor and an anaerobic digestion (AD) reactor. In the AD reactor, the maximum OLR was 4 kg/m3·d whereas the electro-active microbial community in bulk and on the biofilm of the BEAD reactor produced methane even at 10 kg/m3·d. The BEAD reactor rapidly removed volatile fatty acids (VFAs) and reduced H+ to H2 at high OLRs, thereby preventing VFA accumulation and pH decrease. After the steady state was achieved, both the AD and BEAD reactors exhibited similar organic matter removal and methane production at a low OLR. Thus, a BEAD reactor can stably produce methane under conditions of high OLR and severe OLR fluctuation and can even shorten the stabilization period over the long term.