Located on the banks of the Rock River, 90 miles west of Chicago, Rockford Ill., is home to more than 168,000. Since the 1930s the company now known as Layne Christensen has been instrumental in developing Rockford's potable water supply, which is drawn from shallow, unconfined and deep sandstone aquifers through 39 active wells.
When the city needed to bring six wells into compliance with the U.S. Environmental Protection Agency's (EPA) revised Radionuclides Rule, Rockford took the opportunity to improve water quality and determined that five other wells required treatment for higher-than-desired iron and manganese levels. After pilot testing to compare catalytic media with traditional mixed media, LayneOx catalytic media was determined to be the most cost-effective treatment solution.
Rockford’s radium, iron and manganese removal plants were designed by Strand Associates, Inc., Madison, Wis., and Layne was awarded a contract to engineer and fabricate the treatment equipment. The equipment is comprised of eleven plants with treatment capacities ranging from 1,200 gal per minute (gpm) to 2,100 gpm.
The six new radium removal plants will enable Rockford to maintain compliance with the EPA’s Radionuclides Rule. The Rule regulates the combined levels of radium 226/228 to a maximum contaminant level (MCL) of 5 pico Curies per liter (5 pCi/L). Based on pilot tests, typical performance brings a well with median concentrations of 6-10 pCi/L to a treated level of 2 pCi/L, far below the EPA’s MCL.
For the iron and manganese removal plants, currently above the secondary MCLs of 0.30 parts per million (ppm) and 0.05 ppm respectively, the catalytic media enables the filters to operate at a higher loading rate of 6.25 gpm/ft2, with no detention basin and with no need for a permanganate feed. The catalytic nature of the filter media helps with oxidation and the removal of manganese, reducing equipment size, minimizing the accessory equipment required and reducing the building size and cost.
The catalytic filters, engineered and fabricated by Layne, have 30-in. bed depths of LayneOx and use pressure aeration and sodium hypochlorite to oxidize any iron and manganese in the water. Radium is removed using the hydrous manganese oxide (HMO) process. Six of the filters feed HMO to remove radium and any iron or manganese, while five of the filters remove manganese and/or iron from the water. In total, these treatment systems will treat and supply up to 27 million gal per day of potable water. Layne also provided start-up services and operator training.
Today, two of the plants are online and performing within design parameters. The remaining nine plants are scheduled to be in operation by February 2011.