The　study　aimed　at　solving　the　instability　of　shortcut　nitrification-denitrification　through　real-time　control　strategies.　The　results　showed　that　excess　aeration　(aeration　was　still　on　after　nitrosation)　had　an　adverse　impact　on　the　stabilization　of　shortcut　nitrification-denitrification,　with　nitrosation　ratio　(NO(2)(-)-N/NO(x)(-)-N)　decreasing　from　96%　to　29%　after　excess　aeration　for　13　cycles,　indicating　that　excess　aeration　was　prone　to　change　nitrification　modes　from　shortcut　nitrification　to　full　nitrification.　By　using　real-time　control,　shortcut　nitrification　and　full　nitrification　were　clearly　detected　by　characteristic　points　on　ORP　and　pH　curves.　Thus,　aeration　was　stopped　once　nitrosation　was　completed,　and　shortcut　nitrification-denitrification　was　maintained　with　nitrosation　ratio　(NO(2)(-)-N/NO(x)(-)-N)　higher　than　96%.　The　study　showed　that　real-time　control　strategy　could　prevent　excess　aeration　and　achieve　stable　shortcut　nitrification-denitrification.　Crown　Copyright　(C)　2008　Published　by　Elsevier　Ltd.　All　rights　reserved.