The U.S. Army Corps of Engineers (USACE) – Omaha District has funded the design and construction of a new groundwater treatment plant in Cheyenne, Wyoming to treat groundwater from the city’s Borie well field. This important groundwater supply was apparently contaminated with tricholorethene (TCE) in the late 1960s at the Former F.E. Warren Atlas Missile Site 4, several miles southwest and up-gradient of the current Borie well field production wells. The new facility was designed, constructed and placed into long-term automatic operations by Boise, Idaho-based firm McMillen, LLC. Matt Moughamian, McMillen’s project manager says, “For the given application, the most logical and cost effective groundwater treatment choice was low profile air strippers. Air stripping is a simple, reliable, and proven technology for the removal of TCE from water supplies. Furthermore, the air stripping technology was able to be implemented into the city’s existing well field hydraulic profile at a location where repumping of the water was not required. This provided a big advantage and further incentive to use a reliable, low profile air stripping technology, such as that offered by QED E-Z Tray® (U.S. Patent Number 5,518,668) Air Strippers.”
Cheyenne Facility and Field
Current TCE concentration in the Borie well field source can range anywhere between 1 and 25 ppb. In early 2010, the USACE contracted with McMillen to start the final design and construction of the new treatment facility to insure that TCE levels could be reduced to less than 2.0 ppb. A total of four (4), 6-level tray E-Z Tray Air Strippers, each with a treatment capacity of 1,000 gpm, were used in McMillen’s design to insure that the TCE treatment goal of less than 2 ppb could be reached without pretreatment. In Cheyenne’s case, the E-Z Trays do not require off-gas treatment or sequestering agents, making the treatment process fairly simple. The turbulent mixing that occurs in the E-Z Tray units creates a high air to water ratio and large mass transfer surface area resulting in highly efficient contaminant removal. “The water goes straight from the Cheyenne wells into the E-Z Trays, and the Air Strippers have been in constant operation since July 2011 with no need to clean the trays because of buildup or fouling.” Moughamian says. He added that the reliable design and the reasonable price of the E-Z Tray units are great features of QED Air Strippers, but their effective treatment of Cheyenne’s contaminated groundwater and their low profile were the most important features when designing around the E-Z Tray system.