An　anaerobic-aerobic　process　including　a　fresh　refuse　landfill　reactor　as　denitrifying　reactor,　a　well-decomposed　refuse　reactor　as　methanogenesis　reactor　and　an　aerobic　activated　sludge　reactor　as　nitrifying　reactor　was　operated　by　leachate　recirculation　to　remove　organic　and　nitrogen　simultaneously.　The　results　indicated　that　denitrification　and　methanogenesis　were　carried　out　successfully　in　the　fresh　refuse　and　well-decomposed　landfill　reactors,　respectively,　while　the　nitrification　of　NH4+-N　was　performed　in　the　aerobic　reactor.　The　maximum　organic　removal　rate　was　1.78　kg　COD/m(3)　d　in　the　well-decomposed　refuse　landfill　reactor　while　the　NH4+-N　removal　rate　was　0.18　kg　NH4+-N/m(3)　d　in　the　aerobic　reactor.　The　biogas　from　fresh　refuse　reactors　and　well-decomposed　refuse　landfill　reactors　were　consisted　of　mainly　carbon　dioxide　and　methane,　respectively.　The　volume　fraction　of　N-2　increased　with　the　increase　of　NO3-N　concentration　and　decreased　with　the　drop　of　NO3--N　concentration.　The　denitrifying　bacteria　mustered　mainly　in　middle　layer　and　the　denitrifying　bacteria　population　had　a　good　correlation　with　NO3--N　concentration.　(c)　2007　Elsevier　Ltd.　All　rights　reserved.