In this research the process performance of enhanced biological phosphorus removal was investigated in a sequencing batch reactor (SBR) having a new operational mode. The SBR system used in this study had simultaneous feeding and decanting conditions. The laboratory scale reactor (10 L) was operated for 392 days. The system was operated under 4 different sets each having 2 cycles per day. In each cycle, fill (4 h), anoxic (0.5 h), aerobic (7 h) and settling phases were present. In the fill phase, wastewater was fed from the bottom and the anoxic/anaerobic conditions were established in the settled sludge. During filling, the water left the system by water displacement. The system provided nitrification, denitrification as well as phosphorus and organic removal. High COD (90-98%), PO4-P (77-100%), and NH4-N (90-95%) removals were achieved by this system.