Ammonia-induced inhibition of manure-based continuous biomethanation process under different organic loading rates and associated microbial community dynamics

Three Continuously Stirred Tank Reactors (CTSRs) were operating at steady state conditions with Organic Loading Rates (OLR) of 2.09, 3.024 and 4.0 g VS L⁻¹ d⁻¹. Glucose was used as the sole factor for increasing the OLR, linking the increase of the OLR with the C/N ratio increase. The reactors were stressed by increasing the ammonia concentration to 5 g L⁻¹ from 1.862 g L⁻¹. The results showed elevating inhibition of the anaerobic process by increasing the C/N ratio just by increasing the OLR, under the high ammonia concentration. A different response of the bacterial and archaeal community under ammonia stressed conditions was also observed. Under the high ammonia concentration, hydrogen-depended methylotrophic was the dominant methanogenesis route at OLR of 2.09 g VS L⁻¹d⁻¹, while the hydrogenotrophic route was the dominant at the high OLR of 4 g VS L⁻¹d⁻¹, which coincided with high acetate and propionate concentrations.