Integration of double nitrite autotrophic shunt enhances anammox-based wastewater treatment for sustainable nitrogen removal and energy efficiency

Anammox holds significant promise as a next-generation technology for achieving energy-positive wastewater treatment. However, its application remains challenging due to unstable nitrite supply and excessive nitrate residue. To address this, a groundbreaking Anammox bioprocess incorporating a double nitrite autotrophic shunt was developed within single system to realize energy-efficient nitrogen removal from wastewater. Partial nitrification/Anammox converted a portion of ammonia in leachate to nitrogen gas in oxic stage. Significantly, sulfur-driven partial denitrification utilizing sulfide as electron donor, efficiently reduced generated nitrate to nitrite in subsequent anoxic stage, facilitating nitrite reutilization via Anammox and removing residual ammonia. Over 200-day monitoring, bioprocess demonstrated desirable effluent quality with 9.0 mg/L NH4+-N, 0.6 mg/L NO2- -N, and 6.2 mg/L NO3--N. Delightedly, efficient nitrogen removal efficiency of 97.8 % was achieved even under fluctuation conditions. Priority position held by Anammox consortium (Candidatus Kuenenia 11.2 %) mainly derives from similar growth rate of autotrophic bacteria within their shared ecological niche and stable nitrite supply, enabling Anammox to contribute impressive 72.4 % of nitrogen removal. By combing electron flow preference kinetic, stability toward fluctuation, core microbial community, the ecological niche of Candidatus Kuenenia and self consistent logic governing functional microorganisms were revealed. The cost-effective system exhibited significant advantages over conventional bioprocess, reducing organic matter demand by 100 %, aeration energy consumption by 61.7 %, and biomass production by 82.9 %.