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　%.　©　2023　Elsevier　B.V.