In　this　study,　two　bioprocess　models　were　first　constructed　with　the　newly-discovered　comammox　process　described　as　one-step　and　two-step　nitrification　and　evaluated　against　relevant　experimental　data.　The　validated　models　were　then　applied　to　reveal　the　potential　effect　of　comammox　bacteria　on　the　granular　bioreactor　particularly　suitable　for　undertaking　partial　nitritation/anammox　(PN/A)　under　different　operating　conditions　of　bulk　dissolved　oxygen　(DO)　and　influent　NH4+.　The　results　showed　although　comammox　bacteria-based　PN/A　could　achieve　＞　80.0　%　total　nitrogen　(TN)　removal　over　a　relatively　wider　range　of　bulk　DO　and　influent　NH4+　(i.e.,　0.25-0.40　g-O-2/m(3)　and　470-870　g-N/m(3),　respectively)　without　significant　nitrous　oxide　(N2O)　production　(＜　0.1　%),　the　bulk　DO　should　be　finely　controlled　based　on　the　influent　NH4+　to　avoid　the　undesired　full　nitrification　by　comammox　bacteria.　Comparatively,　conventional　ammonium-oxidizing　bacteria　(AOB)-based　PN/A　not　only　required　higher　bulk　DO　to　achieve　＞　80.0　%　TN　removal　but　also　suffered　from　1.7　%similar　to　2.8　%　N2O　production.