A　combined　system　was　developed　to　enhance　the　chemical　oxygen　demand　(COD)　and　total　nitrogen　(TN)　removal　from　landfill　leachate.　The　system　consists　of　an　up-flow　anaerobic　sludge　blanket　(UASB),　anoxic/aerobic　(A/O)　reactor,　and　the　denitrifying　UASB　(DUASB).　The　influent　used　in　our　study　was　a　mixture　of　1:2　raw　leachate　and　domestic　wastewater.　Because　of　the　inhibitory　effect　of　free　ammonia　(FA)　on　the　nitrite-oxidizing　bacteria　(NOB),　stable　partial　nitrification　occurred,　with　a　consistent　nitrite　accumulation　ratio　in　the　A/O　reactor.　In　the　DUASB,　the　nitrite　and　nitrate　nitrogen　(NOX--N)　were　removed　efficiently　by　denitrification　by　utilizing　the　carbon　source　of　refractory　organics　under　anoxic　condition,　which　were　likewise　degraded.　The　organic　matter,　total　nitrogen　and　ammonia　nitrogen　in　the　final　effluent　were　80-90,　39,　and　14　mg/L,　respectively,　with　respective　removal　efficiencies　of　95,　98,　and　95%.　The　respective　COD　removal　efficiencies　in　the　UASB,　A/O　and　denitrifying-UASB　were　76.8,　2.8,　and　16.3%.　The　proposed　process　is　an　advanced　technique　that　accomplishes　the　removal　of　organic　matter　and　nitrogen　in　a　single　step.　(C)　2016　Published　by　Elsevier　B.V.