AWWA ACE54349

On January 22, 2001, the United States Environmental Protection Agency (EPA) finalized the Arsenic Rule with a new maximum contaminant level (MCL) set at 10 ppb. It has been estimated that water supplies for 3,000 community water systems in the United States exceed the 10 ppb MCL. Many of these utilities will be small public water systems. There are several treatment alternatives available for arsenic removal ranging from modification of existing treatment processes to point-of-use, reverse-osmosis systems. Modification of existing processes will be applicable primarily for conventional surfacewater treatment facilities, while point-of-use and point-of-entry systems will be used primarily for extremely small public water systems. In the past, activated alumina (AA) was the most commonly used adsorbent for arsenic removal. Optimal arsenic (anion) removal, for traditional AA occurs in the pH range of 5.5 to 6.0. Reducing the raw water to this level can require a significant quantity of acid for alkaline waters and requires a subsequent pH increase for corrosion control prior todistribution. When the media is exhausted, it is regenerated using sodium hydroxide followed by acid neutralization. The regeneration step produces waste streams that require handling and disposal. The handling and associated costs of the pH adjustments for traditional AA, along with the regenerant waste stream handling and disposal, are important considerations for utilities that may consider the activated alumina process. Furthermore, many utilities will want to forego the regeneration step because of the chemical costs and operational and disposal requirements. A number of iron- and aluminum-based adsorbents recently have been developed to overcome these shortcomings of traditional AA. The American Water Works Association Research Foundation (AWWARF) is sponsoring an ongoing project to demonstrate emerging technologies for arsenic removal including, but not limited to, adsorption. This is the first large-scale, head-to-head comparison of a wide range of promising arsenic removal technologies operating year 'round at the same sites. At the sites where adsorption technology is being demonstrated, the emerging adsorbents being tested include granular ferric hydroxide, iron-modified AA and high porosity AA. This paper presents the testing results collected to date at the City of Scottsdale and the Tucson Water test sites. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2001

Number of Pages:

15

File Size:

1 file , 400 KB