Western Kentucky University

Poster Title

Arsenic Remediation of Drinking Water using Limestone: Contaminant Interference and Surface Morphology

Institution

Western Kentucky University

Abstract

The Environmental Protection Agency (EPA) has proposed lowering the Maximum Contaminant Level (MCL) for arsenic, currently set at 50 ppb or less. Current remediation technologies are expensive. This will result in increased economic pressure on rural communities with high levels of arsenic in their drinking water. The proposed lower MCL for arsenic has spurred the development of appropriate new technologies. This research focused on the development of a remediation technology that has shown the ability to reduce arsenic in drinking water at the source, with added benefit of lowcost disposal of a stable and benign waste product in ordinary landfills. Arsenic, at pH 8.0 and above, is known to be readily soluble and transports easily through ground water. Previous work indicates that arsenic has significant retention in contact with calcium and magnesium carbonates. This could be a result of adsorption on the limestone and dolomite mineral surfaces or precipitation. Adsorption batch tests with crushed limestone have been shown to reduce arsenic from 100 ppb to <5 ppb. Various common drinking water contaminants such as chloride, nitrate, iron, and sulfate were studied to determine the impact on removal efficiency of arsenic. Typically, little interference was found. The temperature dependence of the removal efficiency was also investigated. Scanning Electron Microscopy was used to determine surface morphology of the limestone base and the waste product. Single crystals of arsenic-containing materials were observed. Sintering was also performed to examine the thermal stability of the waste product.

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Arsenic Remediation of Drinking Water using Limestone: Contaminant Interference and Surface Morphology

The Environmental Protection Agency (EPA) has proposed lowering the Maximum Contaminant Level (MCL) for arsenic, currently set at 50 ppb or less. Current remediation technologies are expensive. This will result in increased economic pressure on rural communities with high levels of arsenic in their drinking water. The proposed lower MCL for arsenic has spurred the development of appropriate new technologies. This research focused on the development of a remediation technology that has shown the ability to reduce arsenic in drinking water at the source, with added benefit of lowcost disposal of a stable and benign waste product in ordinary landfills. Arsenic, at pH 8.0 and above, is known to be readily soluble and transports easily through ground water. Previous work indicates that arsenic has significant retention in contact with calcium and magnesium carbonates. This could be a result of adsorption on the limestone and dolomite mineral surfaces or precipitation. Adsorption batch tests with crushed limestone have been shown to reduce arsenic from 100 ppb to <5 ppb. Various common drinking water contaminants such as>chloride, nitrate, iron, and sulfate were studied to determine the impact on removal efficiency of arsenic. Typically, little interference was found. The temperature dependence of the removal efficiency was also investigated. Scanning Electron Microscopy was used to determine surface morphology of the limestone base and the waste product. Single crystals of arsenic-containing materials were observed. Sintering was also performed to examine the thermal stability of the waste product.