Recovery of anammox process performance after substrate inhibition: Reactor performance, sludge morphology, and microbial community

Most of the current studies have focused on the inhibition of anaerobic ammonium oxidation (anammox) by substrates, however, little attention has been paid to the recovery process of the reactor after inhibition. Therefore, we investigated the changes in reactor performance, granular sludge structure, and microbial community during the recovery phase after being inhibited by a high nitrogen load for 15 d. The nitrogen removal rate of the reactor was restored to pre-inhibition levels after 75 d of recovery, and the stoichiometric ratio converged to the theoretical value. The surface of the granular sludge developed into a broccoli-like structure, and the Ca and P contents of the granules increased from 6.88% and 4.39% to 24.42% and 13.88%, respectively. The abundance of the anammox bacterium Candidatus brocadia increased from 5.86% to 12.10%, and network analysis indicated that SMA102 and SBR1031 were positively correlated with the occurrence of Candidatus brocadia.

Automated summary

This study investigated the recovery process of a reactor after being inhibited by a high nitrogen load. The results showed that after 75 days of recovery, the nitrogen removal rate and stoichiometric ratio of the reactor were restored to pre-inhibition levels. The surface structure of the granular sludge changed to a broccoli-like structure, and there was an increase in the Ca and P contents of the granules. Moreover, the abundance of the anammox bacterium Candidatus brocadia also increased, and it showed a positive correlation with specific microbial species.