A　laboratory-scale　anaerobic-anoxic/nitrification　sequencing　batch　reactor　(A(2)N-SBR)　fed　with　domestic　wastewater　was　operated　to　examine　the　effect　of　varying　ratios　of　influent　COD/P,　COD/TN　and　TN/P　on　the　nutrient　removal.　With　the　increased　COD/P,　the　phosphorus　removals　exhibited　an　upward　trend.　The　influent　TN/P　ratios　had　a　positive　linear　correlation　with　the　phosphorus　removal　efficiencies,　mainly　because　nitrates　act　as　electron　acceptors　for　the　phosphorus　uptake　in　the　A(2)N-SBR.　Moreover,　it　was　found　that　lower　COD/TN　ratio,　e.g.　3.5,　did　not　significantly　weaken　the　phosphorus　removal,　though　the　nitrogen　removal　first　decreased　greatly.　The　optimal　phosphorus　and　nitrogen　removals　of　94%　and　91%,　respectively　were　achieved　with　influent　COD/P　and　COD/TN　ratios　of　19.9　and　9.9,　respectively.　Additionally,　a　real-time　control　strategy　for　A(2)N-SBR　can　be　undertaken　based　on　some　characteristic　points　of　pH,　redox　potential　(ORP)　and　dissolved　oxygen　(DO)　profiles　in　order　to　obtain　the　optimum　hydraulic　retention　time　(HRT)　and　improve　the　operating　reliability.　(C)　2009　Published　by　Elsevier　Ltd.