Wednesday, November 10, 2010

Wastewater treatment up to snuff

Bellevue celebrates ribbon cutting at new plant

Express Staff Writer

Seeking advice for his community’s ongoing construction of a similar wastewater treatment plant, American Falls City Council President Norman Wright, left, discusses with Bellevue Public Works Manager George Tanner the choice of air cyclic valves (shown) that work to optimize the feeding environment of micro-organisms employed in the membrane filter of the new Bellevue sewage treatment plant. Photo by Willy Cook

Though there are many "Do Not Drink" signs posted at the new Bellevue wastewater treatment plant, in a pinch the end product—treated sewage—is potable, said Mayor Chris Koch, speaking Friday at a ribbon cutting for the new facility.

"In 2005, we had stringent guidelines that the old lagoon (treatment facility) couldn't meet," Koch said.

The plant is at the longtime site for the city's sewage treatment in an agricultural area off Glendale Road, six miles southwest of downtown Bellevue. At the plant, constructed under the supervision of civil engineers Keller Associates, treated wastewater is applied to agricultural land during the growing season and percolated into the ground during the winter. The old treatment lagoons had regular nitrogen spikes that were 100 times what is allowed by the federal Environmental Protection Agency.

However, nearly $6 million and five years later, Bellevue is finally in compliance with EPA regulations, said Dave Anderson, the engineering regional manager for the Idaho Department of Environmental Quality's Twin Falls office. The regulations govern the treatment of some 300,000 gallons of sewage a day, or about 100 gallons per Bellevue resident.

"They've been working on that for years," Anderson said. "They're now ahead of the curve. They're good for another 20 to 30 years."

Engineers and leaders from as far away as American Falls came to the ribbon cutting to learn more about the state-of-the-art activated sludge processor that includes the use of micro-organisms that consume nutrients in the sewage. The fed organisms, generically called bugs, are then composted at the Ohio Gulch landfill.

"The new membrane holds bacteria and total suspended solids," Anderson said. "They spend more time together and the concentration of the bacteria is a lot higher. We're able to treat to a higher quality."

Bellevue's sewage is treated to 20 parts per million of suspended solids, a Class B level, which allows agricultural irrigation, but not residential irrigation. Drinking-water quality is 10 parts per million. Anderson said some communities in the West achieve five parts per million in an effort to create more opportunities to use wastewater in water-scarce environments. Sun Valley's treatment plant, for example, treats to a Class A level, which will allow that community to reuse water for residential irrigation once infrastructure is in place to distribute it, Anderson said.

With add-on technology, the Bellevue plant could process its water to such cleanliness, but for the time being, the treated resource is designated mostly for agricultural application and for the city's reconditioned rapid infiltration basins to benefit aquifer recharge.

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