Abstract: The purpose of this study was to determine capability of Intermittent Cycle Extended Aeration System (ICEAS) ® (a modification of SBR) to treating contaminants, especially phosphorus. Experiment was carried out in Tehran University of Medical Sciences using a pilot. The used reactor consists of tow zone: pre-react and main react zone. These two zones are separated using a baffle wall. Firstly, wastewater enters to pre-react zone and then through openings in bottom of baffle wall enters to main react zone. The experiment was carried out with three different Hydraulic Retention Times (HRT) and flowrates. Results of different runs showed 38.5, 52.1 and 55.9% of phosphorus removal, which is higher than conventional activated sludge processes. The system is capable to remove phosphorus with nearly similarity with other proprietary phosphorus removal process and with lower cost, whereas is not a proprietary process.