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Nogales International WWTP Upgrade,
International Boundary Water Commission, Nogales AZ

Aeration Basin and Piping prior to Diffuser Installation

Water Works Engineers was a member of the Design-Build team for the $51 million conversion of the 14.74 mgd Nogales International Wastewater Treatment Plant from an aerated lagoon facility to an activated sludge plant. WWE was responsible for the process mechanical design of the activated sludge and solids dewatering facilities. The activated sludge facilities included three parallel trains of concrete aeration basins followed by three 115-foot diameter secondary clarifiers. The facilities were laid out to accommodate the future addition of a fourth aeration basin and clarifier train. The aeration basin was designed with two anoxic cells in series at the head of the aeration basin for Total Nitrogen removal to less than 8 mg/L. Five aerobic zones per train are aerated using fine-bubble diffusers fed by five 400-hp multi-stage centrifugal blowers. A single return activated sludge system utilizing four vertical end-suction centrifugal pumps was set up to provide redundant RAS pumping capabilities.

Waste activated sludge is pumped to two 5-foot diameter rotary drum thickeners for WAS thickening prior to discharge to an aerobic digestion lagoon, where the waste activated sludge is stabilized to Class B requirements. Stabilized sludge flows to a lined storage lagoon (aerated with surface aerators) for equalization, and then dewatered using two 3-belt Belt Filter Presses. The sludge pumping systems allow for operation of the thickener/digester in a recuperative mode to adjust the solids concentration in the digestion lagoon, if necessary.

WWE authored an electronic operations and maintenance manual for the new facility.

3D Model of Three Parallel Aeration Basins as Designed