| Abstract: | ● Simultaneous NH4+/NO3– removal was achieved in the FeS denitrification system ● Anammox coupled FeS denitrification was responsible for NH4+/NO3– removal ● Sulfammox, Feammox and Anammox occurred for NH4+ removal ● Thiobacillus, Nitrospira , and Ca. Kuenenia were key functional microorganisms An autotrophic denitrifying bioreactor with iron sulfide (FeS) as the electron donor was operated to remove ammonium (NH4+) and nitrate (NO3−) synergistically from wastewater for more than 298 d. The concentration of FeS greatly affected the removal of NH4+/NO3−. Additionally, a low hydraulic retention time worsened the removal efficiency of NH4+/NO3−. When the hydraulic retention time was 12 h, the optimal removal was achieved with NH4+ and NO3− removal percentages both above 88%, and the corresponding nitrogen removal loading rates of NH4+ and NO3− were 49.1 and 44.0 mg/(L·d), respectively. The removal of NH4+ mainly occurred in the bottom section of the bioreactor through sulfate/ferric reducing anaerobic ammonium oxidation (Sulfammox/Feammox), nitrification, and anaerobic ammonium oxidation (Anammox) by functional microbes such as Nitrospira, Nitrosomonas, and Candidatus Kuenenia. Meanwhile, NO3− was mainly removed in the middle and upper sections of the bioreactor through autotrophic denitrification by Ferritrophicum, Thiobacillus, Rhodanobacter, and Pseudomonas, which possessed complete denitrification-related genes with high relative abundances. |
