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:
