Roger Evans, a water/sewer mechanic at the water utility, describes the working of a high-lift pump: Water is sucked into the pump and spins through the brass-colored impeller. As the water leaves the pump through large light-blue, horn-shaped volute, velocity is turned into pressure.

At an open house at the City’s water utility on July 26 visitors could see examples of the pipes, pumps, tanks and basins that daily pump about 40 million gallons of safe, clean water into homes and businesses in Evanston, Skokie and elsewhere. The capacity of the utility is more than twice that – 108 million gallons/day.

Evanston’s water utility, 555 Lincoln St., is the “third largest water-treatment plant in the State. It provides 400,000 people with drinkable water [daily],” said Richard Lanyon, a member of the City’s Utilities Commission and retired Evanston alderman.

Water from Lake Michigan reaches the tap after a series of filtering and disinfecting processes, described in greater detail at cityofevanston.org.

Water from the flows by gravity though the intake pipes into three suction wells equipped with screens to remove trash. Here, activated carbon can be added to remove taste and odor, and polymers can be added to aid coagulation. Then six electric centrifugal pumps lift the water from the lake to a level that it can flow by gravity though the treatment plant.

Treatment begins in a flash basin, where liquid aluminum sulfate, chlorine and fluoride are added to the raw water. The chlorine is for disinfection and oxidation of organic materials. The aluminum sulfate forms a precipitate or floc in the water, which causes suspended solids to settle out.

Water then flows to the slow-mix basins, where the chemicals are mixed in. It then runs into the settling basins, where about 90% of the impurities – suspended matter, bacteria and algae, primarily – are removed. It can take at least four and up to eight hours for the floc to settle.

In the next step, rapid filters remove the final traces of turbidity and bacteria. More than 9 million gallons of water can be stored in clear well reservoirs and an underground storage space.

Nine high-lift pumps with a combined capacity of 147 million gallons of water per day, supply water pressure at 50 to 65 pounds per square inch to the distribution system.

The utility has auxiliary engine drives for emergency operations in case of a power failure. In Evanston, two standpipes, one in the north section of town and one in the south, hold a combined 12 million gallons in reserve, and another 10 million gallons are stored in Skokie.

At the open house, Mayor Elizabeth Tisdahl congratulated Utilities Director Dave Stoneback and his staff for their stewardship.

“The Evanston Water Department is the best example of what governments do. We celebrate no only the last 100 years [but] I’d like to celebrate the next 100 years, when Evanston will continue to produce excellent water,” said Mayor Tisdahl.

Mr. Stoneback thanked residents for coming to the open house and pointed with way to guided tours of the utility.

Two milestones in the history or Evanston water were the original commitment to construct the water treatment plant Milestones in Evanston’s Water History and the decision to fluoridate the water. The water pumped by the City between 1894 and 1913 was largely untreated. Lake Michigan was the receptacle for Evanston’s waste and the source its water.

The year after the 1911-12 winter’s typhoid epidemic, the City fathers decided to build a water filtration plant. Construction began in 1913 and the plant was operational in 1914. Evanston’s population grew, as people moved here from Chicago for the clean, safe water.

Three decades later, in the mid-1940s, Evanston – this time with Oak Park – again led the way to safer drinking water with the decision to add fluoride to the drinking water to improve the dental health of children. Periodic follow-ups compared with information of children’s dental health before fluoridation showed “a substantial reduction in carious teeth compared with conditions that existed prior to fluoridation in Evanston and Oak Park, where the water supply was free of fluorine,” according to the Illinois Department of Public Health.