Fast start-up of the anammox process with addition of reduced graphene oxides

In this study, two upflow column reactors were built up to investigate the effects of reduced graphene oxide (RGO) on the startup of anammox process. Continuous experiments indicated that the start-up period of anammox process with RGO addition could be shortened from 67 to 49 days. The further investigation proved that the anammox reactor with RGO addition possessed relatively higher anammox bacteria activity and stronger stability even against the high nitrogen loading rate (NLR) impacting. After 220 days cultivation, the nitrogen removal rate of R2 (RGO addition) reached 1.08 × 103 g-N/(m3 d), which was 27.4% higher than 0.846 × 103 g-N/(m3 d) of the R1 (the control). The hydrazine dehydrogenase (HDH) activity increased dramatically with RGO addition, which could be the trigger of fast anammox start-up. Compared with the control reactor, the quantity of anammox bacteria in R2 increased during the whole operation period by quantitative PCR and fluorescence in situ hybridization analysis.