In 2006, the city of Fond du Lac, Wis., contracted an extensive hydrogeologic study to ascertain the long-term sustainable yield of the city's north and south wellfields, which are completed in the deep sandstone aquifer. The study was designed to help the city evaluate whether it should continue to obtain its municipal water supply from the aquifer, requiring treatment for elevated radionuclide concentrations, or develop a surface water treatment plant to obtain water from Lake Winnebago. Ultimately, the city decided to continue using the deep sandstone aquifer.
The issue then turned to treatment. The raw water provided from 15 existing municipal wells had naturally occurring radium levels exceeding 5 picocuries per liter, and the city needed to treat the water if it was to comply with the revised standard for the U.S. Environmental Protection Agency’s radionuclides rule.
The city contracted with Strand Associates, Inc., Madison, Wis., to design radium removal facilities capable of complying with the radionuclides rule while providing up to 15.4 million gal per day (mgd) of potable water for the city’s population of 42,000.
After one year of pilot tests that compared competing technologies, Layne-Northwest provided Strand with design specifications for inclusion in the overall system design. The treatment scheme was based on filtration with DOWEX Radium Selective Complexer (RSC) , a radium selective adsorption media.
Layne provided four separate radium removal systems treating 15 wells, with a combined treatment capacity of 15.4 mgd. The radium removal facilities were installed at four locations in Fond du Lac. The overall scope of radium treatment included pre-filtration, 20 ASME code-stamped pressure vessels with RSC media, controls for the treatment system and five induced draft aerators to treat radon reduction of the treated effluent.
Under a 10-year service agreement, the company also provides training, removal, replacement and disposal services for the RSC filter media. In addition, the company provides radiation safety officer services and has designed the radiation safety program for the city.