Treatment Process

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Eagle Point Treatment Plant

The Eagle Point Treatment Plant is supplied by five shallow and four deep wells. It serves an average water demand of eight million gallons daily. The treatment facility uses chlorination, fluoridation, filtration, and lime softening processes to comply with all federal and state primary drinking water standards. 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

1. 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.

2. 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.

3. 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.

4. 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.

5. Filtration
Water is then passed through a sand and gravel filter bed, removing any remaining suspended matter.

6. Chlorination
Chlorine is added to disinfect the water. The chlorine helps ensure our water’s microbiological safety by destroying disease-causing organisms.

7. Fluoridation
Fluoride is added to a level of 0.7mg/L to help prevent tooth decay.

8. 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.

9. 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.

10. Distribution
Finished water is pumped directly into the water distribution systems that serve homes and businesses throughout the city of Dubuque.