The typical Orbal® oxidation basin has three concentric channels. The outer channel, where the majority of the process ‘work’ takes place, is an aerated anoxic reactor. The DO of the second channel operates in a swing mode to vary with daily load conditions. The last channel maintains a polishing mode removing remaining BOD and ammonia before the flow exits to final clarifiers. The mechanical backbone is its unique aeration disc with its high oxygen transfer and unmatched mixing efficiency.