Arizona State Department of Corrections,
Lewis Complex Water System Improvements
- Brackish groundwater supply was high in TDS; desalination was required to meet drinking water standards.
- Initial studies determined the use of EDR as the most viable water treatment process.
- Carollo designed the 1.35-mgd EDR treatment plant for the prison complex.
Carollo Engineers was retained in mid-1996 by Arrington Watkins, the architects for the new Lewis State Prison Complex, as a sub-consultant for the design of the required water supply and waste-water treatment facilities.
The water supply for the prison site is a brackish groundwater, with a TDS content of 2,000 to 2,500 parts per million (ppm). As such, desalination was required to meet drinking water standards. Initial studies resulted in the decision to use EDR for the water treatment process.
The design capacity for this treatment plant is 1.35 mgd. For reasons of reliability, and flexibility in production, three (3) independently operating EDR process trains of 450,000 gpd nominal capacity each were installed.
The EDR equipment operates at a recovery rate of 80 to 85 percent. Most of the remaining concentrate water, amounting to 15 to 20 percent, is discharged to lined evaporation ponds approximately 30 acres in size. A small amount of the concentrate from the EDR equipment is blended with effluent from the activated sludge wastewater treatment plant (WWTP) for landscape irrigation.
Additional components of the project included the design of two 1,200 gpm wells. They are reverse circulation rotary drilled 16-inch-diameter casing domestic water wells, with a depth of approximately 1,000 feet.