Effects of increasing organic loading rates on reactor performance and the methanogenic community in a new pilot upflow solid reactor for continuously processing food waste

A new pilot upflow solid reactor (USR) for the anaerobic digestion (AD) of food waste was developed and the reactor performance was investigated. The methanogenic microbial community was examined using high-throughput 16S rRNA gene sequencing technology to identify changes in the community in the new reactor with continuous operation at different organic loading rates (OLRs, from 5.2 +/- 0.5 to 18.8 +/- 0.8 kg COD/(m(3).d)) to help understand the reactor performance. A Methanosaeta-dominated methanogenic community was successfully established when the OLR was between 7.0 and 7.6 kg COD/(m(3).d). Under these conditions, the average COD removal efficiency was greater than 82% and the average methane yield reached a 280 L/kg CODremoval. When the OLR was greater than 18.8 kg COD/(m(3).d), the COD removal efficiency drastically decreased and volatile fatty acids (VFAs) quickly accumulated. The results confirmed that Methanosaeta dominance has a positive effect on reactor performance and methane yield when food waste is treated under an OLR of 7.0 +/- 0.7 kg COD/(m(3).d). This study demonstrates that the microbial population can be manipulated by changing the reaction conditions and the USR, which has a simple structure and operation, has great potential to handle high-OLR food waste. (C) 2020 Published by Elsevier Ltd.