College of Engineering and Natural Science

Northern Arizona University

The Arsenic Terminators

Summary of our Project:


Since January 2006 a new U.S. Environmental Protection Agency primary drinking water standard exists where the maximum contaminant level (MCL) of arsenic (As) is 10 parts per billion (ppb). Several Hopi communities exceed this MCL. The community with the greatest MCL exceedance is Keams Canyon.


 The purpose of this project is to recommend an As adsorption media and to determine the operational and maintenance (O&M) costs associated with an As adsorption treatment train system to be implemented at Keams Canyon to help the community achieve compliance. In order to execute this purpose the following tasks were performed:


Task 1: Water Chemistry Data Collection

Task 2: Adsorption Media Trials

Task 3: Adsorption Treatment Train Research


 Utilizing the results of the water samples collected from Keams Canyon an adsorption media called Granular Ferric Hydroxide (GFH) was selected and tested via laboratory batch tests. During the batch tests the pH, media-to-solution ratio, and media grain size were adjusted to determine the most cost effective combination of these parameters to remove As to well below the MCL. Results proved that GFH absorbs As effectively from the source water. 


 The research for the treatment train involved investigating GFH-compatible equipment and examining all aspects associated with the O&M costs. A full equipment application assessment was provided by Siemens Water Technology Corp. Combining their data with further research it was found that the O&M costs for a system would be $42.5K to $45K depending on the life of the GFH.  


 It is recommended that more batch testing be conducted to develop Freundlich isotherms. Additionally, if time and money allow, Rapid Small Scale Column Tests (RSSCTs) should be performed to more accurately assess the performance of GFH with Keams Canyon water. Once these RSSCTs run optimally it is recommended that the column system be scaled-up to the full treatment size to compare to manufacturers’ equipment sizing to develop the most appropriate treatment train system to be implemented to Keams Canyon. 

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