In 2013, AdEdge Water Technologies was contacted by Valentine Engineering to participate in a design/build project that was ongoing at the Red Rock Correctional Center in Eloy, Arizona. The facility is owned and operated by Corrections Corporation of America, under contract with the Arizona Department of Corrections to administer up to 1,500 prisoners at Red Rock.
Before the contract could begin, the well supplying the facility needed to be treated to potable drinking water standards. It had high levels of total dissolved solids (TDS)—approximately 865 mg/L—and needed to be less than the 500 mg/L secondary maximum contaminant level (MCL) for TDS. A reverse osmosis (RO) system was selected as the best option for removing the high TDS concentrations from the water. The system had to utilize a blend of raw well water into the RO permeate water to produce a final blended water quality with TDS less than 500 mg/L.
The ADRO8-4L-5H reverse osmosis system was custom-designed to allow field upgrade in the future as water usage increases in the facility. The current system produces up to 140 gallons per minute (gpm) of the blended product, with the blend ratio being 80 gpm of RO permeate to 60 gpm of raw good water. The RO system is integrated to the good pump and distribution atmospheric storage tank, prohibiting the RO from running unless water is required in the storage tank.
The system also includes an antiscalant feed system to protect the RO membranes from fouling due to water hardness and silica. A second chemical feed system is integrated and doses sodium hydroxide to the final blended product to increase pH, which will reduce the potential for corrosion in the piping system. A pH controller is interfaced to the RP and chemical feed pump maintaining a final pH in the 7.5 to 7.6 range.
The system was also provided with a clean-in-place (CIP) system, which allows the cleaning of the RO membranes on site without removing them from the RO pressure vessels. The site's operators have been trained to monitor the operating pressure and flow rates, and when certain conditions are reached, the CIP cycle would be performed. CIP cleaning includes the use of low pH and high pH cleaners to primarily remove biofilm and organic scaling due to hardness minerals and silica in the raw well water.
The system was started up and put into operation in February 2014. The system is currently providing a final blended product to the facility with approximately 450 mg/L TDS, meaning the TDS has been treated to below treatment goals since the system began operation.
Case Study Fast Facts
Client: Corrections Corporation of America
Facility: Red Rock Correctional Facility
Engineer: Valentine Engineering
Location: Eloy, AZ
Date: February 2014
Contaminant treated: TDS
Flow rate: 140 gpm