Different inhibition patterns of ammonia and salt revealed by kinetic analysis of their combined inhibitory effect on methanogenesis of hydrogen: A preliminary study

Kinetic parameters of the inhibitory effect of ammonia and salt on anaerobic digestion remain unclear. We investigated the combined inhibition effect of ammonia and salt on anaerobic digestion through hydrogen-fed specific methanogenetic activity (SMA) tests. The kinetic parameters estimated using mathematical models indicated a concentration-dependent monotonical SMA decrease caused by both ammonia and salt, but a different inhibition pattern was determined for each inhibitory factor. A 3-D contour analysis indicated that the combined inhibitory effect of ammonia and salt depended on both their concentrations. Salinity was proposed as a unified parameter for predicting the combined inhibition, and a maximum of 3.5% was observed for methane production. Thus, this study provides a detailed perspective on the combined inhibitory effect of ammonia and salt on methanogenesis of hydrogen. Further investigation into different kinds of seed sludge and inhibition mitigating experiments could enhance the stability of the anaerobic digestion process.