This study is an analysis about BOD ,COD, SS, T-N, T-P of 4Stage-BNR, MLE + CS(Coagulating Sedimentation) , Bio-SAC BNR method of construction for 3 largest sewage treatment plants among 12 sewage treatment plants in lncheon. The purpose of this study is improving the operational effectiveness for lncheon sewage treatment plant by introducing the optimized method for quality of the discharged water.