Effect of exogenous folate addition on the start-up process of single-stage partial nitritation-anammox system

In this study, two lab-scale reactors were operated to evaluate the impact of exogenous folate on the start-up process of single-stage partial nitritation-anammox (SPNA). Folate at a dose of 0.5, 1.0, and 1.5 mg/L was continuously added into the experimental reactor (RI) at different operation stages. The highest nitrogen removal rate was 0.26 kg N/(m3 center dot d) in RI with a nitrogen loading rate of 0.45 kg N/(m3 center dot d), which was higher than that in the control reactor (RII) of 0.20 kg N/(m3 center dot d). Moreover, the extracellular polymeric substances production in RI with 1.5 mg/L folate dosage was 264.24 +/- 6.74 mg/gVSS, enhancing by 0.5-fold that of the RII, and the activity of hydrazine oxidase increased to the highest level of 0.37 +/- 0.01 mu mol cyt-c/(gVSS center dot s). Meanwhile, the activity of dehydrogenase in RI was enhanced from 796.39 +/- 2.19 mu g/(gVSS center dot min) to 819.17 +/- 24.47 mu g/(min center dot gVSS). The relative abundance of Candidatus Brocadia was 0.64 % at the end of phase 5 in RI whereas it remained at 0.25 % in RII. Function prediction showed that the nitrogen-related genes highly increased with the folate addition.

Automated summary

In this study, the impact of exogenous folate on the start-up process of single-stage partial nitritation-anammox (SPNA) was evaluated using two lab-scale reactors. The results showed that folate addition can enhance nitrogen removal rate, extracellular polymeric substances production, hydrazine oxidase and dehydrogenase activity, as well as the relative abundance of Candidatus Brocadia.