Center for Groundwater Science - Arsenic in Illinois Groundwater, Illinois State Water Survey

Center for Groundwater Science

Arsenic in Illinois Groundwater

The United States Environmental Protection Agency (USEPA) recently lowered the allowable maximum contaminant level (MCL) for arsenic from 50 micrograms per liter (μg/L) to 10 μg/L. This new regulation applies only to public water supplies and does not affect the hundreds of thousands of private wells in use in Illinois. However, arsenic concentrations above the MCL are found in many aquifers in Illinois; thus private wells may be vulnerable to arsenic contamination. Data are needed to determine if high levels of arsenic are found in private wells in Illinois.

In September 2001, the Illinois State Water Survey (ISWS) and Waste Management Research Center (WMRC), with funding from WMRC, began an 18-month study to look at arsenic levels in private wells in Tazewell and Champaign Counties. This study will allow researchers to look at why some areas have more arsenic in their drinking water than do others, as well as to determine what factors affect the mobility of arsenic in groundwater. The study also includes an examination of existing public water treatment systems to determine how water chemistry affects arsenic removal and to evaluate the relative success of existing treatment systems in removing arsenic.

In a related study set to begin in early 2002 with funding from the Midwest Technology Assistance Center (MTAC) for Small Public Water Supplies, the ISWS will be sampling 40 public water supplies throughout Illinois to evaluate how well existing treatments remove arsenic under varying chemical conditions. In addition, the study will include the testing of two experimental treatment processes that potentially will aid small communities in lowering the arsenic levels in their finished water.

Arsenic in Illinois Groundwater discusses the main issues relevant to arsenic in Illinois groundwater, including costs for public supplies that will require additional treatment to meet the new MCL, options for private well owners, and a description of why arsenic is a concern and where it exists in Illinois' groundwater. The paper was written cooperatively by staff of the ISWS, the Illinois Environmental Protection Agency, and the Illinois Department of Public Health.

Distribution of Arsenic in the Mahomet Aquifer, presented as a poster at the Fall 2001 Geological Society of America meeting, summarizes available arsenic data in the Mahomet Aquifer of central Illinois. Preliminary estimates of the spatial distribution of arsenic were made, and these data were the basis for the current research efforts now under way at the ISWS.

For more background information about arsenic in groundwater and the new arsenic regulation:

Contact our Center Head for more information.

Illinois State Water Survey

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Champaign, IL 61820-7463

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