Skip common site navigation and headers
United States Environmental Protection Agency
Exposure Research
Begin Hierarchical Links EPA Home > Research & Development > Exposure Research > Publications/Presentations > End Hierarchical Links

 

Stability: An Investigation of As(iii)/As(v) Stability in Iron Rich Drinking Water Matrices

spacer
spacer
Abstract:Arsenic in drinking water is predominantly inorganic arsenic. The two oxidation states of inorganic arsenic are As(III)(pKa=9.3) and As(V)(pKa2=6.9). The distribution of As(III) and AS(V) in a water is dependent on the redox potential of the water. The actual distribution can vary considerably with a general rule that high percentages of As(III) are ususally associated with ground wqters while high percentages of As(V) are generally associated with surface waters. Current drinking water regulatins do not differentiate between these two oxidation states when setting the maximum contaminate level (MCL) for arsenic. The need to differentiate As(III) and As(V) arises from a treatment/removal perspective within the drinking water regulations. Certain treatment strategies remove As(V) more efficiently than As(III). Therefore, treatment engineers usually require a speciation based analysis before designing a treatment strategy. The accuracy of this analysis is strongly dependent on how well the native distribution of As(III) and As(V) is preserved prior to analysis. Factors which can influence the preservation are dissolved oxygen, iron preciption, temperature, time and biological actvity. The precipitation of iron is an important factor because it can change the distribution and the contration of aqueous arsenic. In addition, there is a geological correlation between arsenic and iron, thus the iron precipitaiton factor is quite common. In an attempt to preserve the native arsenic distribution in iron rich waters we have been investigating the use of EDTA in combination with acidification with acetic acid (HAc). This presentation will focus on the use of EDTA/HAc in a number of well waters from across the US. The stability of the EDTA/HAc treated samples will be investigated over time and compared to controls and non-treated samples. The overall change in the distribution will be reported with a special emphasis on how these changes affect the treatment decision making process.
spacer
Citation:Gallagher, P. A., J. T. Creed, C. A. Schwegel, A. Heck, and B. M. Gamble. Stability: An Investigation of As(iii)/As(v) Stability in Iron Rich Drinking Water Matrices. Presented at International Ion Chromatography Symposium, Chicago, IL, September 9-12, 2001.
spacer
spacer
Contact: Mary P. O'Bryant - (919)-541-4871 or obriant.mary@epa.gov
spacer
Division: Microbiological & Chemical Exposure Assessment Division
spacer
Branch: Chemical Exposure Research Branch
spacer
Product Type: Abstrct/Oral
spacer
Presented: 09/12/2001
spacer
Related Entries:
spacer
Bullet Item In-Field Preservation of Arsenic Species in Drinking Water Using Edta
spacer Relationship Reason:   A Project of the Product
spacer
spacer
spacer

 

ORD Home | Search EPA | Search NERL | Search EIMS | Contacts | Help

 
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us

Last Updated on Monday, October 22, 2007
URL: http://cfpub.epa.gov