Promotion of the start-up of the anammox reactor with exogenous boron

In this study, boron, an essential element of interspecies quorum sensing (QS) signals, was first proposed to enhance the start-up of the anaerobic ammonium oxidation (anammox) process. Exogenous boron was added into the anammox reactor, and its effect on the ammonia removal, granulation, AI-2 QS, and microbial community was examined. The results showed that the total nitrogen conversion rate in the experimental upflow anaerobic sludge blanket (UASB) with exogenous boron added (denoted as e-UASB) was 0.7 & PLUSMN; 0.05 kg N m(-3) d(-1), approximately three times that in the control UASB without boron (0.23 & PLUSMN; 0.05 kg N m(-3) d(-1), denoted as c-UASB). The exogenous addition of boron elevated the AI-2 concentration, increased the content of extracellular polymeric substances (EPS), and promoted granulation in the UASB during start-up. Microbial community analysis indicated that the abundances of anammox bacteria, i.e. Candidatus Brocadiales and Candidatus Jettenia, in the e-UASB were much higher than those in the c-UASB (25.5% vs. 19.7%). Additionally, Anaerolineaceae, which is known to play an important role in the granulation of anammox bacteria, had an abundance of 21.13% in e-UASB and 17.74% in c-UASB. It is demonstrated that exogenous boron could be promising in enhancing the start-up of an anammox reactor through promoting QS, granulation, and anammox.

Automated summary

In this study, the effect of exogenous boron on the start-up of the anaerobic ammonium oxidation (anammox) process was investigated. It was found that the addition of boron significantly increased the total nitrogen conversion rate and promoted granulation in the system. Additionally, boron elevated the AI-2 concentration and affected the microbial community, leading to higher abundances of anammox bacteria and Anaerolineaceae.