Thursday, June 2, 2011
Ion Exchange Removes Uranium
by TJ Stroebl
Tonka Equipment Company
Bridgeport, a town of 1594 people, is located in Western Nebraska equidistant among Sidney, Alliance, and Scottsbluff. Not long ago, Bridgeport was pumping water directly out of the ground and into the distribution system, with no treatment required. It was then discovered that the water had elevated levels of uranium, and treatment would be required. The town worked with their engineer, Olsson Associates, to come up with a solution to handle the situation.
A natural element and a byproduct—two sources of uranium in water
Uranium normally exists naturally in groundwaters, slowly dissolved over time from soils and sedimentary rock. It also can be a byproduct of fertilizer application, mining activity, and combustion. Uranium is classified as a human carcinogen and is known to cause kidney toxicity; thus it is regulated by the Environmental Protection Agency as a primary contaminant. The maximum contaminant level MCL is set at 30 μg/L.
Olsson Associates chose Tonka and its ion exchange as the removal technology for Bridgeport’s solution. Bridgeport’s supply has a pH range above 6.5, so uranium appears as large and negatively charged carbonate complexes, which can be removed via ion exchange. Tonka Equipment Company was selected to conduct a pilot study to prove out the selected ion exchange technology. Tonka erected pilot equipment on site and trained personnel from the both the Town and Olsson Associates in its operation. Bridgeport personnel operated the equipment for approximately three months, regularly performing field tests and taking samples for lab analysis. The pilot test showed consistent uranium removal to well below the MCL, allowing the engineer to confidently proceed with a Tonka full-scale system design.
Safe drinking water for Bridgeport
The three 8’ diameter vessels in Tonka’s ion exchange system treat raw water containing 78 μg/L of uranium. This operator-friendly system regenerates once per month, with a finished water quality that reduces the carcinogenic contaminant to levels well below the MCL, providing the people of Bridgeport with quality water.