Effects of Fe3+ on microbial communities shifts, functional genes expression and nitrogen transformation during the start-up of Anammox process.

Abstract In this study, the effect of Fe3+ on the start-up of Anammox process was investigated. Four EGSB reactors were operated with the addition of 0 (R1), 0.04 (R2), 0.08 (R3) and 0.14 (R4) mmol/L Fe3+, respectively. The results showed that Fe3+ remarkably improved the nitrogen loading rate (NLR) and operation efficiency of the reactor. After 180 days, the influent NH4+-N concentration in the four reactors was 201.4, 301.8, 343.2, 380.2 mg N/L, and the NLR was 589.3, 877.6, 993.0, 1105.8 mg N/(L·d), respectively. And the nitrogen removal rate (NRR) in R2, R3 and R4 was respectively 1.54, 1.73 and 1.94 times of that in R1. High throughput sequencing revealed that Fe3+ could promote the enrichment of Anammox bacteria Candidatus Brocadia. Moreover, the analysis by qPCR indicated that the abundance of Anammox 16S rRNA gene and the functional gene hzsB increased, which showed a positive correlation with the concentration of Fe3+.