As part of a multi-faceted, nearly $7 million upgrade of its drinking-water supply system, Fairfield, Iowa, has built a new water treatment plant. The facility, which has a capacity of 2 million gallons per day (mgd), uses a process called electrodialysis reversal (EDR) to remove impurities from raw water. The plant began operations in April and reduces the demand on a nearby 4-mgd lime-softening water-treatment plant that the city has used for years.

Until the late 1990s, Fairfield relied heavily on three local lakes for its drinking-water supply. However, the surface water posed several problems for the city, such as high turbidity, a tremendous amount of algae and lots of microorganisms, says Dennis Langstraat, general superintendent for Fairfield Water Works.

“[The water] smelled really bad,” Langstraat says, referring to the pre-treated water. Sometimes, the offensive smells made their way to the customers' taps, and the city was hit with complaints about taste and odor problems. Adding to the Water Department's headaches were stringent state and federal surface-water regulations.

In 1999, Fairfield began using only groundwater from the Jordan aquifer, a large water-bearing sandstone formation that lies under much of eastern Iowa. The city had been drawing some of its drinking water from the aquifer since the late 1950s. The groundwater, however, contains a high mineral content, and the city began looking for a more effective method than lime softening to remove the impurities. In June 2002, construction of the new plant began. Fairfield purchased an EDR 2020 system from Watertown, Mass.-based Ionics for approximately $3 million to use in the plant.

Water from the aquifer is piped into the plant and first passes through a cartridge filter that removes sand and other fine particles. The water then goes through a series of membranes that remove ions such as sulfates, chlorides, and salts. Some membranes remove positively charged ions, while others remove negatively charged ions.

After it leaves the EDR plant, the water is mixed with water from the lime-softening plant and then piped into Fairfield's distribution system. Each plant supplies approximately half of the city's total daily supply of water. Fairfield currently produces about 2.5 mgd of drinking water each day, but that figure could increase later in the year if hot and dry weather conditions are prevalent, Langstraat says.

“EDR is a lot better for removing [minerals] than lime softening,” Langstraat says. “Lime softening is a little cheaper. The combination works out very well and produces a good blended product.” The treated water contains less than 700 parts per million of total dissolved solids — nearly a 50 percent reduction from the pre-treated water.

Fairfield has not used the EDR plant to increase its total daily water supply. The city simply has used the facility to change its treatment process. Other components of the city's overall water-supply upgrade included the construction of a 2,000-gpm well, the replacement of century-old water mains and various improvements to the lime-softening plant.