Linkage between reactor performance and microbial community dynamics was investigated during
mesophilic anaerobic co-digestion of restaurant grease waste (GTW) with municipal wastewater sludge
(MWS) using 10 L completely mixed reactors and a 20 day SRT. Test reactors received a mixture of GTW
and MWS while control reactors received only MWS. Addition of GTW to the test reactors enhanced the
biogas production and methane yield by up to 65% and 120%, respectively. Pyrosequencing revealed that
Methanosaeta and Methanomicrobium were the dominant acetoclastic and hydrogenotrophic methanogen
genera, respectively, during stable reactor operation. The number of Methanosarcina and Methanomicrobium
sequences increased and that of Methanosaeta declined when the proportion of GTW in the feed was
increased to cause an overload condition. Under this overload condition, the pH, alkalinity and methane
production decreased and VFA concentrations increased dramatically. Candidatus cloacamonas, affiliated
within phylum Spirochaetes, were the dominant bacterial genus at all reactor loadings.