A　laboratory-scale　anaerobic-anoxic-aerobic　process　(A(2)O)　with　a　small　aerobic　zone　and　a　bigger　anoxic　zone　and　biologic　aerated　filter　(A(2)O-BAF)　system　was　operated　to　treat　low　carbon-to-nitrogen　ratio　domestic　wastewater.　The　A(2)O　process　was　employed　mainly　for　organic　matter　and　phosphorus　removal,　and　for　denitrification.　The　BAF　was　only　used　for　nitrification　which　coupled　with　a　settling　tank　Compared　with　a　conventional　A(2)O　process,　the　suspended　activated　sludge　in　this　A(2)O-BAF　process　contained　small　quantities　of　nitrifier,　but　nitrification　overwhelmingly　conducted　in　BAF.　So　the　system　successfully　avoided　the　contradiction　in　sludge　retention　time　(SRT)　between　nitrifying　bacteria　and　phosphorus　accumulating　organisms　(PAOs).　Denitrifying　phosphorus　accumulating　organisms　(DPAOs)　played　an　important　role　in　removing　up　to　91%　of　phosphorus　along　with　nitrogen,　which　indicated　that　the　suspended　activated　sludge　process　presented　a　good　denitrifying　phosphorus　removal　performance.　The　average　removal　efficiency　of　chemical　oxygen　demand　(COD),　total　nitrogen　(TN),　total　phosphorus　(TP),　and　NH　(4)　(+)　-N　were　85.56%,　92.07%,　81.24%　and　98.7%　respectively.　The　effluent　quality　consistently　satisfied　the　national　first　level　A　effluent　discharge　standard　of　China.　The　average　sludge　volume　index　(SVI)　was　85.4　mL　center　dot　g(-1)　additionally,　the　volume　ratio　of　anaerobic,　anoxic　and　aerobic　zone　in　A(2)O　process　was　also　investigated,　and　the　results　demonstrated　that　the　optimum　value　was　1:6:2.