In　this　study,　a　bench-scale　Cyclic　Activated　Sludge　Technology　(CAST)　reactor　(72?L),　fed　with　domestic　sewage,　was　operated　in　alternating　anoxic-aerobic　operation　mode　to　investigate　the　feasibility　of　achieving　short-cut　nitrification　and　denitrification　with　a　real-time　control　strategy.　An　online　system　for　controlling　the　length　of　the　aeration　and　stirring　phases　was　implemented,　based　on　pH　and　oxidation-reduction　potential　signals,　to　switch　between　aerobic　and　anoxic　sequences.　Results　show　that　the　real-time　control　strategy　was　successful　in　achieving　a　stable　nitrogen　removal　performance.　Furthermore,　short-cut　nitrification　can　be　achieved　by　controlling　aeration　length　under　the　modified　real-time　control　strategy.　Gradually　reducing　the　energy　supply　for　nitrite-oxidizing　bacteria　caused　the　limitation　of　their　growth　and,　finally,　their　elimination.　When　short-cut　nitrification　was　obtained,　the　nitrite　pathway　became　the　primary　way　for　nitrogen　removal,　and　aeration　duration　was　reduced　by　28.4%.