When the Environmental Protection Agency dropped the maximum contaminant level for arsenic in public drinking water from 50 micrograms per liter (µg/L) to below 10 µg/L in 2006, cities throughout Oklahoma that had been using the Garber-Wellington Aquifer for their groundwater for decades became noncompliant.
In the City of Norman alone, 11 of the three dozen wells were taken offline, cutting the average well production from nearly 5 million gallons per day to barely 2 mgd and reducing the municipality's water supply during peak months.
Garver, LLC acted as project manager and design engineer for a turn-key wellhead arsenic removal system at the city's well No. 31, one of several that tested as high as 70 µg/L. The Severn Trent Services SORB 33 Arsenic Removal System - which uses adsorbent iron oxide media to effectively and economically remove arsenic - became the first of its kind in Oklahoma.
The Garber-Wellington Aquifer typically has yielded 100-500 gallons of drinking water per minute per wellhead. The naturally occurring arsenic in the aquifer is separated from the drinking water through a variety of techniques consisting of adsorption, occlusion, and solid-solution formation that reacts with ferric oxide ions.
The system sends pressurized water through a stationary filter vessel that contains a ferric oxide media. Arsenic is attracted to the media, and the water is reduced to a compliant level below 7 µg/L. The dry, crystalline granular media is designed to adsorb much of the arsenic to achieve long operating cycles. Once it is expired, the media is sent to a non-hazardous landfill.
American Public Works Association Congress & Exposition
Session: Reclaiming water and revenue through wellhead arsenic removal
Mon., Aug. 16, 2010
Mary Elizabeth Mach, project engineer