An　innovative　partial　nitrification,　in　situ　fermentation,　and　Anammox　(PNFA)　system　was　developed　to　achieve　mature　landfill　leachate　and　waste　activated　sludge　simultaneous　treatment.　Three　separate　sequencing　batch　reactors　(SBRs)　were　used　for　partial　nitrification　(PN-SBR),　integrated　fermentation-denitrification　(IFD-SBR),　and　partial　nitrification-Anammox　(PNA-SBR).　After　200　days　of　continuous　operation,　a　satisfactory　nitrogen　removal　efficiency　(NRE)　of　99.2　+/-　0.1%　was　obtained,　with　an　effluent　total　nitrogen　(TN)　of　15.2　+/-　3.2　mg/L.　In　IFD-SBR,　the　volatile　fatty　acids　generated　from　fermentation　drove　efficient　denitrification,　obtaining　sludge　and　nitrogen　reduction　rates　of　4.2　+/-　0.7　and　0.61　+/-　0.04　kg/m(3).day,　respectively.　Furthermore,　unwanted　fermentation　metabolites　(134.1　mg/L　NH4+-N)　were　further　treated　by　PNA-SBR　using　a　combination　of　step-feed　and　intermittent　aeration　strategies.　In　PNA-SBR,　Anammox　significantly　contributed　to　82.1%　nitrogen　removal,　and　Anammox　bacteria　(Candidatus　Brocadia,　2.3%)　mutually　benefited　with　partially　denitrifying　microorganisms　(Thauera,　4.2%),　with　66.3%　of　generated　nitrate　reduced　to　nitrite　and　then　reutilized　in　situ　by　Anammox.　Compared　with　the　conventional　nitrification-denitrification　process,　PNFA　reduced　oxygen　energy　consumption,　external　carbon　source　dosage,　and　CO2　emission　by　21.3,　100,　and　38.9%,　respectively,　and　obtained　50.1%　external　WAS　reduction　efficiency.