Osmoprotectants boost adaptation and protect methanogenic microbiome during ammonia toxicity events in continuous processes.

Different osmoprotectants were used to counteract ammonia toxicity in continuous anaerobic reactors. The anaerobic microbiome osmoadaptation process and its role to the methanogenic recovery are also assessed. Three osmoprotectants (i.e., glycine betaine, MgCl and KCl) were respectively introduced in continuous reactors at high ammonia levels, namely R, R, R, while a control reactor (R) was also used. After ammonia was introduced, the R, R, R and R suffered 39.0%, 36.6%, 39.9% and 36.2% methane production loss, respectively. Osmoprotectants addition recovered significantly methane production by up to 68.9%, 54.3% and 32.2% for R, R and R, respectively contrary to R, where production increased only by 13.6%. The recovered methane production was maintained in R and R for at least four HRTs, even after the addition of osmoprotectants was stopped, due to the formed methanogenic microbiota by osmoadaptation process, with Methanoculleus sp. as the dominant species.