Somerton Wastewater Treatment Plant Expansion

Somerton, Arizona

Kiewit was selected by the City of Somerton for the expansion of their sequential batch reactor (SBR) wastewater treatment plant. Prior to the design commencing, Kiewit performed cost modeling and constructability reviews to aid in the determination that a biological nutrient removal process (BNR) design would be more beneficial than the original concept. Kiewit provided anticipated construction costs and schedules for the conversion of the existing and additional SBRs to a BNR. These side-by-side comparisons allowed the selection of the best value expansion approach for the plant. The BNR approach was selected and increased the current from .8 to 1.8 million gallons per day for an addition of 6 million gallons per day in capacity from the original concept.

The expansion consisted of construction of two new 60-inch diameter WesTech secondary clarifiers with return/waste activated sludge pump station. A masonry dewatering building addition was constructed complete with two Huber screw press units, an Enpro polymer feed system and Grundfos booster pumps for solids handling to replace the removal of the existing sludge drying beds. Work also included a new motor control center, electrical elements, and instrumentation to accommodate the plant expansion and conversion.

Additionally, the existing aeration basins received new Aerostrip diffuser systems, conveyance piping and a concrete-formed channel. Other work included improvements to the chlorine contact basin, influent pump station and digesters, and installation of service water booster pumps.