Research Highlights

Successful Technologies for Arsenic Removal From Drinking Water

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When the federal rule limiting arsenic in drinking water was revised in 2001 to 10 parts per billion, it challenged nearly all small U.S. water systems (those serving 10,000 or fewer people) to find cost-effective ways to meet the new standards. Recognizing the potential economic and technical burdens of compliance, EPA proposed a number of assistance programs. One of these is the Arsenic Removal Technology Demonstration Program, initiated in 2002 to provide cost-effective technologies, training, and technical assistance for small systems. Directed by National Risk Management Research Laboratory (NRMRL) drinking water scientists, the first round of the demonstration program matched 12 small utilities with the best-fit arsenic removal technologies in order to gather performance and cost data that could be shared with other U.S. communities. Round 2 of the program identified 28 additional sites and Round 2a another 10 sites, bringing the total to 50 (see map). All 50 systems are expected to be installed and operating by summer of 2008.

Map identifying location of sites involved in Arsenic Removal Technologies program.

Background

Arsenic is a human carcinogen. Chronic exposure to low levels of arsenic has been linked to skin, kidney, lung, and bladder cancers, as well as adverse neurological and cardiovascular effects. The erosion of natural deposits of arsenic, common to many areas of the U.S., is a potential source of ground water contamination, and thus, of local drinking water. Other exposure sources are pesticide runoff from orchards, and industrial wastes from glass and electronics production. By the 1990s, the development of increasingly sophisticated detection tools highlighted the risks of arsenic in drinking water and prompted the federal reduction of arsenic standards from the initial 50 parts per billion to a safer 10 parts per billion, which became effective by 2006.

For most small drinking water systems, installing new treatment technologies depends on a variety of factors: the quality of source water, the ease of integration into existing systems, the management of treatment wastes, and costs. EPA’s Arsenic Removal Technology Demonstration Program worked with selected small systems (chosen through a competitive voluntary process) to identify the best arsenic removal technology for each community from a variety of commercially available products. Technologies were offered free of charge during the demonstration and, if successful, were available to communities at no cost upon completion of the study. Local systems paid for any new construction required for housing the equipment and for the waste disposal process, plus personnel and operating costs.

In the Town of Climax

Some of the most successful studies were conducted in communities with source water rich in iron because of the strong affinity of natural iron surfaces for adsorbing arsenic. An example is the agricultural community of Climax, Minnesota, about 300 miles northeast of Minneapolis, population 270. The iron-based technology selected by the Climax water system involved a three-step process of oxidation, precipitation/coagulation, and filtration. The demonstration results were dramatic: from a previous level of 36–38 parts per billion, arsenic levels dropped to 4–6 parts per billion in treated water, putting the Climax utility well within the mandated federal limits. Furthermore, the technology equipment occupied minimal physical space, was affordable, and required little maintenance. The arsenic treatment had the added benefit of reducing the naturally occurring iron in the water—from a previous level of 500–850 parts per billion down to 25–30, resulting in reports from some homeowners of increased water flows at the faucet. Following the demonstration period, the community elected to keep the technology permanently.

Because of the variability of source water across the U.S. and differences in small systems operations, there is no “one-size-fits-all” technology for arsenic removal. However, NRMRL researchers to date have published the results of more than 25 technology demonstrations that are providing important arsenic removal information to small systems managers, state and local governments, and technology vendors nationwide.

Contact

Jane Ice, NRMRL Office of Public Affairs (513) 569-7311