Impact/Purpose:

To develop an in-field preservation strategy for As(III) and As(V) in iron rich drinking waters which will allow samples to be shipped to the laboratory for arsenic speciation analysis. The overall goal is to improve treatment decision making and in turn minimize exposure to arsenic resulting from the consumption of drinking water.

Description:

The two predominant inorganic arsenic species found in drinking waters are As(III) and As(V). As(III) is commonly associated with ground waters while As(V) is associated with surface waters. The efficiency of arsenic removal from a drinking water supply is dependent on the oxidation state of the arsenic because the removal technology is often based on anion exchange or iron co-precipitation. Because As(V) is an anion at drinking water pHs, the removal of As(V) is more quantitative relative to As(III) which is non-anionic and unretained by anion exchange treatment. Furthermore, As(III) and As(V) are a redox couple and for this reason they can readily interconvert if the oxidative or reductive properties of the water change prior to analysis. For example, the native distribution can be altered by changes in dissolved oxygen and dissolved iron present in the drinking water. Thus, the preservation of the native As(III)/As(V) is an essential piece of information used in treatment decision making in order to optimize the removal of arsenic. Preliminary data collected using EDTA to complex the iron has indicated that As(III) and As(V) are stable for greater than 30 days in iron rich waters. Therefore, EDTA treatment appears to allow iron rich drinking water samples to be shipped to the laboratory for analysis while preserving the native As(III)/As(V) concentration. This task evaluated this preservation process by applying it to several "real world" waters supplies. Ultimately, a preservation strategy will be implemented in the field prior to shipment which will prevent species interconversion until laboratory analysis can be completed. This in-field preservation will aid in arsenic treatment decision making by providing an As(III)/As(V) concentration which reflects that associated with the native water.

Record Details:

Record Type:PROJECT

Start Date:10/01/2000

Completion Date:09/30/2002

Record ID: 19936

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Project Information:

Progress :The research under this task is complete (an additional publication based on this research - the in-field preservation of inorganic arsenic species in iron rich drinking water sources - will be submitted to a peer reviewed journal by September, 2003). In summary,

A procedure was developed to separate and identify arsenic species using ion chromatography with inductively coupled plasma - mass spectrometry (presented at SEGH, 98).

Preservation data was presented at a number of scientific conferences - (SEGH 98), (Winter Conference, 00) (ICCS, 01).

Research indicated that EDTA prevents arsenic losses in iron rich waters (JEM, 2001). The EDTA treatment (described in JEM,2001) has been utilized in the field (on 5 independent well waters) and has demonstrated good As(III) and As(V) stabilities for greater than 30 days (presented at ICCS, 2001).

Papers/Presentations produced under this task:

-Creed, J., Schwegel, C. and X. Wei, "Arsenic speciation in Drinking Water Matrices Via IC-ICP-MS", SEGH, 8/98, San Diego, CA.

-Creed, J., Gallagher, P., Shoemaker, J., Wei, X., and C. Brockhoff, "Speciation of Drinking Water Contaminants by IC-ICP-MS", presented at Jekyll Island Symposium, May 1999, Jekyll Island, GA.

-Schwegel, C., Gallagher, P., Wei, X., and J. Creed, "Speciation and Preservation Studies of Inorganic Arsenic in Drinking Water Sources Using IC-ICP/MS", presented at Winter Conference on Plasma Spectrochemistry, January 2000, Ft Lauderdale, FL."

- Creed, J., Wei, X., Gallagher, P. and C. Schwegel, "Use of EDTA for Preservation of Arsenic Species in Iron Rich Drinking Water Sources", presented at the American Water Works Association Meeting, November 5-9, 2000, Salt Lake City, Utah.

- Gallagher, P., Schwegel, C., Wei, X. and J. Creed, "Speciation and Preservation of Inorganic Arsenic in Drinking Water Sources Using EDTA with IC Separation and ICP-MS Detection," published in the Journal of Environmental Monitoring, 3, 371-76, 2001.

- Gallagher, P., Schwegel, C., Heck, A., Gamble, B. and J. Creed, "An Investigation of As(III) / As(V) Stability in Iron Rich Water Matrices " presented at ICCS, Chicago, IL 2001.



Relevance :Relevance: The Office of Research and Development has designated the study of arsenic as a high priority research area because of the health risk associated from exposure to this element. The research described in this task is identified in the Arsenic Research Plan (ARP) as Exposure Issue 1. Therefore, this task is relevant to the Agency's mission in that it addresses scientific shortcomings identified in the ARP and supports treatment decision making which ultimately minimizes exposure to arsenic from drinking water ingestion. Significance: The reduction in the arsenic maximum contaminant level (MCL) from 50ppb to 10ppb will require noncompliant drinking water supplies to implement some type of treatment to reduce exposures. The research described in this task will improve the efficiency of arsenic removal by providing treatment engineers with accurate information regarding the redox mixture present in the untreated water. The need for effective treatment decision making will grow in its significance as the emphasis of the arsenic rule shifts from drafting legislation to implementation and ongoing compliance. Impact: Compliance implies added treatment costs and these costs are directly impacted by poor or inaccurate treatment decision making. The need to comply with the arsenic rule will in some cases require the "tweeking" of existing removal strategies while wholesale changes in the treatment may be necessary. Decisions made on poor analytical results can mislead treatment engineers and in turn affect overall costs and ultimately influence the effectiveness of the removal and exposure of arsenic through drinking water consumption. Collaboration and Customer Interaction: From the inception of this project, the PI has collaborated with NRMRL who has provided NERL with field samples. Through routine (every other month) informal meetings, the progress, results and the need for future samplings are discussed. The collaboration with NRMRL has also resulted in the identification of additional issues (i.e, media evaluation and pipe scale characterization) which will be initiated in FY02 in a separate task. In addition, the PI participates on an American Water Works Association Research Foundation Project Advisory Committee (AWWARF PAC) for the in-field speciation of arsenic and through this has been exposed to some AWWA issues and research conducted at USGS. The PI has been invited to sit on an upcoming AWWARF PAC on the preservation of arsenic. Through these interactions with AWWARF and NRMRL, the research efforts conducted in this task have been refocused and refined to address treatment needs. Finally, communication is maintained with the Office of Ground Water and Drinking Water in order to determine research needs and provide information which could impact future arsenic drinking water regulations. This exchange is accomplished through teleconferences, through communication with NERL's ALD for Drinking Water or through exchange of research results.

Clients :Office of Ground Water and Drinking Water (Ireen Dooley and Jennifer Wu)

Research Component :ARSENIC

Risk Paradigm :EXPOSURE

Project IDs:

ID Code :none

Project type :ORD-DW Plan

ID Code :10910

Project type :OMIS