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EXTRACTION AND SPECIATION OF ARSENIC CONTAINING DRINKING WATER TREATMENT SOLIDS BY IC-ICP-MS
Citation:
CREED, JOHN T., P. A. CREED, C. GALLAWA, AND C. A. SCHWEGEL. EXTRACTION AND SPECIATION OF ARSENIC CONTAINING DRINKING WATER TREATMENT SOLIDS BY IC-ICP-MS. Presented at 2006 Winter Conference on Plasma Spectrochemistry, Tucson, AZ, January 08 - 14, 2006.
Impact/Purpose:
To assess the stability of "FeOOHAs" residues in existing drinking water distribution systems and drinking water generated wastes.
Description:
In 2001, the U.S. Environmental Protection Agency (EPA) passed the Arsenic Rule, which established a maximum contaminant level of 105g/L. Compliance with this regulation has caused a number of drinking water utilities to investigate potential treatment options. The adsorption of arsenic onto iron oxide-hydroxides via coagulation is one of the most common means of achieving arsenic removal. Some of the arsenic containing solids formed during coagulation (treatment related or natural) may enter the distribution system because of inadequate filtration. Compliance with the Arsenic Rule may cause some drinking water utilities to alter basic water quality parameters such as pH and phosphate. This may affect the mobility of the arsenic on the distribution system solids. One factor that could influence the mobility is the oxidation state of the arsenic attached to the solids. Therefore, an improved understanding of the oxidation state of the adsorbed arsenic is critical to assessing these solids as potential exposure sources. The oxidation state of the arsenic on these solids can be estimated by either X-ray Absorption Near Edge Structure (XANES) or on-line sequential extraction coupled with IC-ICP-MS. The latter is a cost effective means of evaluating the oxidation state of the arsenic associated with these solids. To date, the sequential extraction technique has been used to estimate the As(III)/As(V) on iron based treatment media used to enhance removal efficiencies within drinking water treatment plants. This presentation will extend this application to arsenic containing distribution system solids which have recently been shown to contain elevated levels of arsenic.[1]