Synergistic ammonia and nitrate removal in a novel pyrite-driven autotrophic denitrification biofilter

Pyrite is one kind of cost-effective electron donors for nitrate denitrification. In this study, a pyrite-driven autotrophic denitrification biofilter was applied for simultaneous removal of NH4 (+) and NO3- over the 150-day. The influent NH4+/NO3- ratio (0.3-1.7) had less effect on system performance, while for the hydraulic retention times (HRTs, 24-3 h), the removal percentage of both > 90% and removal loading rates of 52.8 and 59.4 mg N/(L.d) for NH4+ and NO3- removal were obtained at the HRT of 6 h. The 16S rRNA genes analysis showed that Ferritrophicum, Thiobacillus, Candidatus_Brocadia, and unidentified_Nitrospiraceae were predominant. Analyses of nitrogen and sulfur metabolism showed that ammonia was removed by complete nitrification, nitrate was reduced to N-2, and sulfide was oxidized to sulfate. Dynamics of pollutants within the reactor and microbial activity showed nitrification/Anammox and pyrite-driven autotrophic denitrification were responsible for the synergistic removal of NH4+/NO3- in this system.

Automated summary

This study applied a pyrite-driven autotrophic denitrification biofilter for simultaneous removal of NH4(+) and NO3- and investigated the factors influencing system performance and analyzed the dominant microbial populations and nitrogen and sulfur metabolism. The results showed that the nitrification/Anammox reaction and pyrite-driven autotrophic denitrification synergistically removed NH4(+) and NO3-.