Construction of autotrophic nitrogen removal system based on zero-valent iron (ZVI): performance and mechanism

In this study, the performance and mechanism of nitrogen removal in sequencing batch reactors (SBRs) with and without zero-valent iron (ZVI) was investigated. The results showed that ZVI had a capacity to promote NH4+-N conversion, NO2--N accumulation and total inorganic nitrogen (TIN) removal, with the TIN removal rate being increased by 29.45%. The ZVI also had a significant impact on microbial community structure by means of high-throughput pyrosequencing, increasing the enrichment of Anammox (anaerobic ammonium oxidation) bacteria Candidatus Brocadia and Feammox (anaerobic ferric ammonium oxidation) bacteria Ignavibacterium. With ZVI addition, the main pathway of nitrogen removal was changed from nitrification-heterotrophic denitrification to Anammox and Feammox.