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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Final Progress Reports: University of Arizona: Arsenic in Water: Removal Technologies and Residuals Disposal

Superfund Research Program

Arsenic in Water: Removal Technologies and Residuals Disposal

Project Leader: Wendell P. Ela
Grant Number: P42ES004940
Funding Period: 2005-2010

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Final Progress Reports

Year:   2009 

Arsenic is removed from water by adsorption onto solids that are most commonly composed of iron. Earlier research has shown that when these iron solids are disposed of in municipal landfills, the arsenic is readily mobilized off of the solid and back into surrounding water bodies. This project investigated the causes of this arsenic release and developed strategies to prevent arsenic mobilization. The researchers' studies show that arsenic mobilization is a complex process: experiments indicate that most of the arsenic is released much later than the iron and that the fraction of the arsenic released is much greater than the fraction of the iron released. The results suggest that microbes play a crucial role, causing either iron dissolution or arsenic release. Under conditions similar to those found in a mature landfill, researchers found that dissolved iron and arsenic re-precipitate, forming crystalline minerals. The researchers' experiments with non-iron based sorbents that do not dissolve under landfill conditions found similar arsenic release rates that are comparable to those found with iron-based sorbents. Because of the ease of release of arsenic from the solids used for arsenic treatment, the team investigated means to stabilize the solids so that they would retain the arsenic after landfill disposal. Previously, the researchers demonstrated that a polymeric encapsulation process could be used to stabilize the arsenic on the solids, and they now are studying how the polymeric encapsulated solids perform under landfill conditions. After almost two years in a simulated landfill, the encapsulated solids have released only a small fraction of the arsenic mobilized from the original sorbent. This suggests that the technology developed in this project has great potential as a practical tool in the control of arsenic mobilization.

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