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Effects of Arsenic Valence and Well-Water Chemistry on Arsenic Removal Efficiencies of Household Water Treatment Systems
Presentation (pdf document)
Charles W. Culbertson1, James M. Caldwell1, Lorraine C. Backer2, Carol Haskins3, Diane Daigle3 and Andrew E. Smith3
1 USGS, Maine District, Augusta, ME
2 Centers For Disease Control and Prevention, Atlanta, GA
3 Maine Centers for Disease Control, Bureau of Health, Augusta, ME
Arsenic in ground water is linked to a variety of serious human health issues worldwide. While elevated arsenic concentrations typically arise from geologic sources, the mechanism(s) by which arsenic is mobilized depends largely on ground water chemistry. Arsenic in ground water occurs primarily in the inorganic form, as pentavalent arsenate, or trivalent arsenite. The oxidation state of arsenic in well water greatly affects its removal by water purification systems. Arsenate, having a strong ionic charge, adsorbs to many surfaces and is therefore easily removed by a variety of water treatment technologies; in contrast to arsenite, which is relatively un-charged over a broad pH range, making it more weakly adsorbant and therefore the more mobile and difficult form to remove.
Roughly half of Maine’s population derives its water from domestic wells, most of which are drilled bedrock wells. The U.S. Geological Survey, in cooperation with the Maine Centers for Disease Control, and U.S. Centers for Disease Control and Prevention are investigating the effects of arsenic valence and well-water chemistry on arsenic removal efficiencies of household water purification systems in selected households in Maine. Households participating in this study employed several technologies for removing arsenic from their water supplies. The presence of arsenite required different removal strategies compared to the removal of arsenate. Results of this ongoing study will be presented and discussed.
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