Innovator: Treatment Plant Celebrates 75 Years of Secondary Treatment

Coeur d’Alene’s treatment facility had biological treatment 33 years ahead of the first Clean Water Act.
Innovator: Treatment Plant Celebrates 75 Years of Secondary Treatment
The Coeur d’Alene (Idaho) Wastewater Treatment plant —commissioned in 1939 — was among the first in the Northwest, and one of few in the nation at the time, to offer secondary treatment.

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Clean-water plant anniversaries are often routine affairs, marking little more than the passage of years.

There’s much more to the 75th anniversary of the Coeur d’Alene (Idaho) Wastewater Treatment plant. The facility, commissioned in 1939, was among the first in the Northwest, and one of few in the nation at the time, to offer secondary treatment. Back then, some communities simply sent their sewage into the rivers untreated, and many had plants providing only preliminary and primary treatment.

The city marked the plant’s anniversary on Friday, Aug. 1, with a free hot dog and hamburger lunch. An open house from 9 a.m. to 3:30 p.m. included hourly tours for ages 10 and up and a presentation on “What Happens After the Flush.”

“Fun, games and crafts for kids are also planned,” according to an article in the Coeur d’Alene Press, and “Visitors…will be able to visit the plant’s laboratory and watch videos of microorganisms feeding on sewage.”

Early innovations
When the treatment plant opened in 1939, Coeur d'Alene was home to about 10,000, and many homes were on septic systems, according to the newspaper. Sid Fredrickson, wastewater superintendent and winner of the Pacific Northwest Clean Water Associations’ 2013 William D. Hatfield Award, told the paper the plant went online 20 years before the one in Spokane, Wash.: “We were ahead of the game.”

In a history of the city’s wastewater utility, Fredrickson wrote, “The Coeur d’Alene wastewater treatment plant … was initially a secondary plant. The primary portion consisted of headworks with screening and disinfection with chlorine, and a flocculator followed by a single primary clarifier. The secondary portion consisted of a rock-media trickling filter followed by a secondary clarifier. The final effluent was not initially chlorinated for disinfection before being discharged to the Spokane River through an open pipe that ended about 200 feet from shore.

“There was separate grit removal in the flocculator. There was a natural- or digester-gas-fired incinerator to dispose of the screenings. Primary and secondary sludge was sent to two digesters; first to a primary and then into the secondary. Digested sludge then went to sludge-drying beds. Final biosolids disposal was achieved by making the product available to the citizens and land application on city property.”

Moving forward
When Fredrickson started with the city in 1986, much of the original treatment process was still in place. Since 1982, the plant has seen 11 major upgrades. Today, Coeur d’Alene is home to about 46,000, and the treatment plant is being upgraded to provide tertiary treatment for phosphorus removal, using membrane microfiltration (ZeeWeed technology from GE Power & Water). The plant now has a design capacity of 6 mgd.


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