Uranium is a naturally occurring element, but that does not mean it should be in drinking water; in parts of Kansas, natural and human-caused conditions have combined to result in groundwater contamination.
Uranium Water Quality Standard
Uranium is a naturally occurring radioactive element that can be found in the ambient soil, found more commonly in the western states. It is no surprise that the residents of a number of communities in Kansas have been drinking water with uranium levels above the USEPA water quality standard. When the EPA set their drinking water standard for uranium to 30 ppb in December 2003, some Kansas communities were unable to meet the standard. The Water Quality Rules found in the community’s National Pollutant Discharge Elimination System (NPDES) Permit states that if a community is unable to make the standard, then the USEPA requires quarterly monitoring for four years of the element until the standard is met. This did not happen for these Kansas communities. They are now out of compliance with the EPA's water quality standard, and as a result they are now expected to find ways to lower the uranium concentration in the drinking water.
Where Did The Uranium Come From?
Some of the communities in question are found along the Arkansas River and others were outside the Arkansas River Valley. The main water source in this region of western Kansas is the High Plains aquifer (of which the Ogallala aquifer is a part), which is fed by water from the Colorado portion of the Arkansas River watershed. The uranium-rich water orginates from the Cretaceous-age shales that were deposited more than 65 million years ago in Colorado. The rivers transport the uranium to the aquifers in Kansas. Before the uranium-contaminated water makes it into Kansas, according to Don Whittemore, a Kansas Geological Survey geochemist, the water is diverted in Colorado to reservoirs and is also used to irrigate fields. While there it has a higher exposure to the elements allowing for evaporation and transpiration which inadvertently increases the concentrations of the naturally occurring element.
Human Health Effects Of Uranium Exposure
At the low concentration levels of uranium that the USEPA uses for the water quality standard, uranium is not considered a public health risk. As the concentration increases above the standard so, too, does the risk to human health. Most of the uranium consumed is actually excreted from the body, but some is still absorbed into the blood stream and carried to the kidneys. At the higher concentrations, uranium can cause an increased risk to kidney damage and to developing cancer. Presumably, the radioactivity of the uranium is not a concern at these low concentration levels.
How To Reduce The Uranium Levels
Once drinking water is out of compliance with the EPA (after the 4 year grace period) the municipalities are responsible for lowering the uranium concentration in the drinking water. The EPA recommends using additional water treatment schemes to bring the water into compliance. In the case of a privately owned well, an anion exchange or reverse osmosis treatment system is recommended to reduce the uranium to acceptable concentrations. On the larger scale, EPA recommends public systems to use lime softening and enhanced coagulation with filtration or diluting the uranium concentration by adding water from a different source.
"Uranium" Los Alamos Laboratory: http://periodic.lanl.gov/elements/92.html
"High Plains Home" Kansas Geological Survey: http://www.kgs.ku.edu/HighPlains/index.shtml
"Arkansas River Watershed" Earthtrends: http://earthtrends.wri.org/maps_spatial/maps_fullscale.php?mapID=391&theme=2