Water Treatment

Eagle Point Treatment Plant
Treatment DiagramThe Eagle Point Treatment Plant is a groundwater, lime softening, water treatment plant. Starting with source water that is virtually free of sediment, the lime softening process reduces the total hardness from about 280 mg/L to 100 mg/L. 

Treatment Process Overview
  • Aeration - Raw or untreated water is drawn from wells into the City’s treatment plant and is cascaded down through a series of trays, increasing the surface area of the water and promoting the exchange of gases. Aeration also removes undesirable gases such as radon. Aeration is similar to the natural process that occurs when a stream flows through rapids or over falls.
  • Flocculant Aid Addition - An anionic flocculant aid is added just after aeration. The flocculant helps to improve the clarity of the water by allowing fine particles to clump together and settle out.
  • Softening - Calcium oxide (lime) is mixed with water to form slaked lime. This slaked lime is then added to the water to soften or reduce the minerals that typically make water hard. Excessive hardness increases soap use, deposits scale in water heaters and boilers, interferes with some industrial processes, and sometimes gives water an unappealing taste and odor. The byproducts from the softening process are applied to farmland as a soil conditioner.
  • Recarbonation - The addition of slaked lime increases the pH of the water to about 10. In order to stabilize the softened water, the pH must be lowered. This pH reduction is accomplished by adding carbon dioxide until the pH is approximately 9.3.
  • Filtration - Water is then passed through a sand and gravel filter bed, removing any remaining suspended matter.
  • Chlorination - Chlorine is added to disinfect the water. The chlorine helps ensure our water’s microbiological safety by destroying disease-causing organisms.
  • Fluoridation - Fluoride is added to a level of 0.7mg/L to help prevent tooth decay.
  • Phosphate Addition - Phosphate is added to chemically stabilize the water and lessen the possibility that lead will leach out of pipes and into tap water.
  • Reserves - Water not immediately consumed flows into storage tanks for use when demand exceeds plant pumpage. Water stored in elevated tanks helps stabilize pressure in the distribution system and serves as an emergency reserve for fire protection.
  • Distribution - Finished water is pumped directly into the water distribution systems that serve homes and businesses throughout the city of Dubuque.