Microbial driving mechanism for simultaneous removal of nitrogen and phosphorus in a pure anammox reactor under ferrous ion exposure

The mechanisms of Fe2+ on nitrogen and phosphorus removal and functional bacterial competition in anammox systems was investigated. Under 0.12 mM Fe2+, the performance of nitrogen and phosphorus removal increased by 10.08 % and 151.91 %, respectively, compared with the control stage. Phosphorus removal was achieved through extracellular polymeric substance (EPS) induced biomineralization to form Fe-P minerals, and functional group C-O-C in EPS played a critical role. T-EPSs was the major nucleation site due to it maintaining the supersaturated state (saturation index > 0) of Fe-P minerals for a long time. Population succession showed that Fe2+ weakened the competition between heterotrophic denitrifier (Denitrasoma) and anammox microbe (Can-didatus Brocadia) for space and substrates, which was favorable for the enrichment of anammox biomass. Moreover, the variation in gene abundance (such as Hao, Cyt c, and Nir) indicated that Fe2+ improved electron behaviors (generation, transport, and consumption) during the nitrogen metabolism of anammox systems.

Automated summary

This study investigated the mechanisms of Fe2+ on nitrogen and phosphorus removal and functional bacterial competition in anammox systems. The results showed that under 0.12 mM Fe2+, the removal performance of nitrogen and phosphorus increased by 10.08% and 151.91%, respectively. Phosphorus removal was achieved through biomineralization induced by extracellular polymeric substances (EPS), with the functional group C-O-C in EPS playing a critical role. Fe2+ weakened the competition between heterotrophic denitrifier and anammox microbe, which facilitated the enrichment of anammox biomass. Furthermore, Fe2+ improved electron behaviors during the nitrogen metabolism of anammox systems.