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Wastewater treatment microbes ready to make journey to new Willmar plant

Construction work is nearly complete at Willmar's new wastewater treatment plant. The next stage is colonizing the new facility with the millions of microbes that digest and break down municipal waste -- a process that could temporarily create odor at the old plant. Tribune photo by Gary Miller

WILLMAR -- The buildings are ready, the pipeline has been installed, the tanks and ditches are in place.

The next stage in completing Willmar's new multimillion-dollar wastewater treatment plant involves one of the more arcane steps in the process: colonizing the new facility with the millions of microbes that digest and break down municipal waste.

Rhonda Rae, program manager with the Willmar office of Donahue and Associates, the engineering consultants for the wastewater treatment plant, outlined for the Willmar City Council on Monday night how this will take place.

Starting in early August, the microorganisms that populate the old wastewater treatment plant on the southeast side of Willmar will be pumped through an interceptor line to the new facility west of town. The organisms are contained in a mixture of sludge and effluent that will be flushed through the line daily, Rae said.

Once this slurry arrives at the new treatment plant, the microbes will be allowed to settle out and multiply in the oxidation ditches.

"This process should take up to four weeks, if not six," Rae told the City Council.

But be forewarned: The biochemical balance at the old wastewater treatment plant, which will continue to handle the city's wastewater until the new facility is up and running this fall, might be temporarily disrupted, resulting in some odor, Rae said.

"So we should be prepared for some phone calls?" wondered council member Rick Fagerlie.

City officials have reason to be a little apprehensive. Odor problems have plagued the existing wastewater treatment plant for much of its history. The persistent bad smell even triggered a lawsuit in the 1980s by neighboring property owners.

Rae tried to reassure the council that engineers would do their best to minimize the odor while the microbe population is redistributed.

"I'm not going to guarantee no odors," she said.

Odor will likely be an issue for only a few days or, at most, a week, she said.

The engineering consultants know that neighboring businesses and residents want to know what to expect, Rae said. "We will try to keep everybody informed as much as possible."

Meanwhile, another step in the process -- the decommissioning of the existing wastewater treatment plant -- moved forward with the opening of bids Tuesday. The administration building will be remodeled to house some staff who will continue to be stationed there, but much of the remaining facility will be demolished.

The contract is scheduled to be awarded at the Aug. 2 meeting of the City Council.

Anne Polta

Anne Polta covers health care, business/economic development and general assignment. Her HealthBeat blog can be found at Follow her on Twitter at @AnnePolta.

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