In　order　to　investigate　the　effect　of　volumetric　exchange　ratio　on　nitrogen　removal　in　novel　UniFed　SBR　process,　two　UniFed　SBR　reactors　were　operated　at　the　volumetric　exchange　ratio　of　25%　and　42%　respectively　to　treat　real　domestic　wastewater.　The　effect　of　volumetric　exchange　ratio　on　nitrogen　removal　was　analyzed　by　comparing　the　degradation　rules　of　TN　during　a　whole　cycle　and　TN　concentrations　of　effluent　at　6　group　identical　feed　ρ　(C)/ρ　(N)　ratios　at　25%　and　42%　respectively.　The　results　showed　that　when　UniFed　SBR　process　was　operated　at　any　volumetric　exchange　ratio,　a　corresponding　maximum　TN　removal　efficiency　η1max　during　feed/decant　period　always　existed.　η1max　was　only　relative　to　volumetric　exchange　ratio　and　irrespective　of　feed　ρ　(C)/ρ　(N)　ratio.　When　the　carbon　sources　of　influent　were　sufficient,　the　bigger　the　volumetric　exchange　ratio,　the　lower　η1max　was.　When　at　the　same　feed　ρ　(C)/ρ　(N)　ratio,　the　bigger　the　volumetric　exchange　ratio,　the　higher　TN　removal　efficiency　was.　TN　removal　during　feed/decant　period　contributed　more　to　UniFed　SBR　process,　so　the　use　of　smaller　volumetric　exchange　ratio　was　beneficial　to　TN　removal　of　the　whole　process.