Abstract: A method of treating wastewater using an aeration tank of the type having an interior divided into at least a first chamber and a last chamber with each of the chambers having a lower portion and an upper portion and having liquid passageways in the lower portions of each of the chambers and gas passageways in the upper portions of each of the chambers for allowing liquid and gas to pass sequentially through each of the chambers from the first chamber to the last chamber, having an effluent outlet associated with the last chamber of the aeration tank for allowing treated water to exit the aeration tank; and having agitator means to enhance oxygen transfer from the upper portion to the lower portion of the aeration tank.

Abstract: An aerobic wastewater treatment system including an aeration tank, the interior of the aeration tank being divided into at least a first chamber and a last chamber, each of the chambers having a lower portion and an upper portion; structure for allowing influent wastewater to be treated and return sludge to enter the lower portion of the first chamber of the aeration tank; structure for allowing mixed liquor to flow sequentially through the lower portions of each of the chambers; an effluent outlet associated with the last chamber of the aeration tank for allowing mixed liquor to exit the aeration tank; agitator structure associated with each chamber of the aeration tank for enhancing oxygen transfer from the upper to the lower portions of each chamber; structure for introducing high-purity oxygen into the first chamber of the aeration tank and for maintaining the pressure in the upper portion of the first chamber of the aeration tank to at or below existing atmospheric pressure; structure for controlling gas