In this research an experimental plant was constructed and operated in order to study the efficiency of the intermittent aeration activated sludge system that operated at the ratio of (On/Off aeration times) (15min/15min), (30min/30min), (60min/60min), (90min/90min) and (120min/120min) and compare their performance with the continuous flow extended aeration activated sludge. The results of the study revealed that; extended aeration reactor is more efficient in removing organic matter than the intermittent aeration reactors. At the hydraulic detention times of (24, 18 and 32), 100%, 65% and 100% of effluent readings had organic concentration less than the acceptable effluent level in compare to 75%, 60% and 80% at the (90min/90min) reactor. In comparison of On/Off aeration times, (90min/90min) reactors provide the best organic removal. All readings from the extended aeration and (15min/15min), (60min/60min), and (90min/90min) reactors were within the acceptable level for effluent suspended solids while the effluent concentrations from the (120min/120min) reactors were higher. The results also indicated that, intermittent aeration reactors are better in removing phosphorous than the extended aeration. At the detention times of 24 and 18 hours, 8% and 6% of readings from the extended aeration reactors had (PO4 ≤ 5 mg/l) in compare to 90% and 52% of readings from the (60min/60min) reactor. At detention time of 32 hours, 32% of readings from the extended aeration reactor had (PO4 ≤ 2 mg/l) in compare to 72% for the (60min/60min) reactor. Higher phosphorus removals were recorded at (60min/60min) reactors.