Based　on　the　anoxic/oxic　(A/O)　step　feed　process,　a　modified　University　of　Cape　Town　(UCT)　step　feed　process　was　developed　by　adding　an　anaerobic　zone　and　adjusting　sludge　return　pipeline.　Performance　evaluation　of　these　two　types　of　processes　was　investigated　by　optimizing　operational　parameters,　such　as　the　anaerobic/anoxic/oxic　volumes,　internal　recycle　ratios,　and　sludge　retention　times,　for　removal　of　chemical　oxygen　demanding　(COD),　nitrogen,　and　phosphorus.　Results　showed　high　removal　efficiencies　of　COD　of　(85.0　+/-　1.7)%,　ammonium　of　(99.7　+/-　0.2)%,　total　nitrogen　(TN)　of　(85.5　+/-　1.7)%,　phosphorus　of　(95.1　+/-　3.3)%,　as　well　as　excellent　sludge　settleability　with　average　sludge　volume　index　of　(83.7　+/-　9.5)　L　center　dot　mg(-1)　in　the　modified　UCT　process.　Moreover,　(61.5　+/-　6.0)%　of　influent　COD　was　efficiently　involved　in　denitrification　or　phosphorus　release　process.　As　much　as　35.3%　of　TN　was　eliminated　through　simultaneous　nitrification　and　denitrification　process　in　aerobic　zones.　In　addition,　the　presence　of　denitrifying　phosphorus　accumulating　organisms　(DNPAOs),　accounting　for　approximately　39.2%　of　PAOs,　was　also　greatly　beneficial　to　the　nitrogen　and　phosphorus　removal.　Consequently,　the　modified　UCT　step　feed　process　was　more　attractive　for　the　wastewater　treatment　plant,　because　it　had　extremely　competitive　advantages　such　as　higher　nutrient　removal　efficiencies,　lower　energy　and　dosages　consumption,　excellent　settling　sludge　and　operational　assurance.