Impact of acetate and propionate on anammox process in an expanded granular sludge bed: Evaluation of microbial community dynamics

Two expanded, granular sludge bed reactors were operated to investigate the effect of acetate acid (R1) and propionate acid (R2) on the anaerobic ammonium oxidization (anammox) process. It was indicated that low acetic acid (30 mg/L) and propionic acid (21 mg/L) concentration enhanced the performance of the two reactors. The heterotrophic denitrification process began to dominate when the organic acid concentration reached 270 and 191 mg/L, and the relative abundance of the heterotrophic denitrifying genus (Rubrivivax) increased from 0.5% and 3.3-6.2% and 8.9%, which the contribution of anammox in R1 and R2 was reduced to 43.62% and 68.08%, respectively. Better recovery efficiency in R2 was found after stopping adding acetate acid and propionate acid. The elevated relative abundance of ATP-blinding cassette transporters and membrane and intracellular structural molecules is the pattern of anammox bacteria (AnAOB) in response to organics inhibition. That explains the increase of abundance and gene copy number of the AnAOB genus (Candidatus Brocadia). AnAOB restored energy supply through the carbon fixation pathway and citrate cycle. Dok59 and Rubrivivax were the major heterotrophic denitrifying genus, with the latter preferring to use propionic acid.

Automated summary

This study found that low concentrations of acetic acid and propionic acid can enhance the performance of the anammox process. When the organic acid concentration is too high, heterotrophic denitrification begins to dominate. Under organic inhibition, anammox bacteria restore energy supply through the carbon fixation pathway and citrate cycle.