Effect of Continuous and Intermittent Aeration Modes on the Efficiency of the Continuous Flow Extended Aeration Activated Sludge Systems

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.