Background
The Ramah Navajo Chapter owns and operates the Ramah Pine Hill water system located in Ramah, N.M. The water system is served by one well that provides drinking water for the community’s residents at a maximum of 130 gal per minute (gpm) with an approximate arsenic concentration of 18 ppb and high iron concentration of 1.7 mg/L.
In order to meet the U.S. Environmental Protection Agency (EPA) maximum contaminant level of 10 ppb, the site engineers, Souder Miller, worked with AdEdge Technologies to size, design and furnish a solution. AdEdge worked with SRS Construction, the Ramah Navajo Chapter’s chosen contractor, to supply an arsenic and iron water treatment system capable of reducing the high arsenic and iron concentrations in the water supply well.
Treatment System
AdEdge installed an APU26-3060-3-AVH oxidation/filtration unit capable of treating the design flow. The packaged skid-mounted system features three 30-in.-diameter carbon steel adsorption vessels mounted on a carbon steel skid utilizing AdEdge AD26 catalytic media . The AD26 oxidation/filtration approach utilizes the naturally high iron in the groundwater to aid in removal of the arsenic.
The system includes a chlorine feed pretreatment module to aid in oxidation and is equipped with automated control valves and harness, a central control panel with programmable logic controller and a color user-interface touch screen. The system also features a hydraulic panel with local gauges, flow sensors and totalizers, and sample ports for a complete functioning packaged unit. The system control panel also provides controls and interlocks with booster pumps, a water truck fill station card reader and a building security system. The system was designed to accommodate and facilitate a future connection to a much larger distribution system, as planned by the Indian Health Service.
Results
After system installation in early 2009, a one-week full arsenic test was conducted to demonstrate system performance and to fine-tune system parameters due to unexpectedly high groundwater temperatures and turbidity. The system continues to remove arsenic to nondetectable levels, to remove iron to less than 0.05 mg/L and to remove manganese to less than 0.02 mg/L—significantly below the standards.
