November 2, 2012

Sewage odors prompt study of plant

After a rise in complaints and a meeting with East End residents, officials look into smell solutions.

By Randy Billings
Staff Writer

(Continued from page 1)

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A condo building on the Eastern Prom overlooks Portland’s wastewater treatment plant. Preliminary recommendations from sewage odor consultants for how to reduce bad smells from the plant will be presented to city residents next week.

John Ewing/Staff Photographer

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People now call or send emails, but they don't give enough information for workers to trace the problem.

An online form is being created to ask for the day, time and weather conditions when odors are detected.

"We do want to understand what odors, and when those odors are experienced, so we can figure out what's causing them," Firmin said.

The plant will also draft an odor-control plan, so it can easily communicate its efforts to the neighborhood, he said.

Bowker, owner of Bowker & Associates, said three primary odors are associated with phases of treating wastewater.

Raw sewage can typically smell like rotten eggs, he said, while wastewater going through the clarification process can have a "musty, earthy odor."

A strong sulphur odor can be produced in the processing of residual material -- or the sludge of pollutants.

The $2.5 million system for removing odor is working as well as it did when it was put in, Bowker said. The dual-stage system treats the smelly air twice, removing 99 percent of the stench.

An air scrubber that treats odor during the second -- and smelliest -- half of processing is not working as well, he said. That air scrubber is used for the sludge.

"Out of all the odor sources, sludge-handling was one of the strongest," Bowker said.

The $2.5 million air scrubber was part of a $7.6 million overhaul of the plant to capture and control odors.

The project included building domes over raw-sewage holding tanks.

Bowker, who has consulted with treatment plants throughout the United States, said the East End Treatment Plant has better odor controlling systems than 90 percent of the plants he has seen.

"That's one of the things that's so frustrating -- to hear there has been this rash of odor complaints over the summer," said Bowker, who in 25 years has never encountered an odor-free treatment plant.

Firmin said the district is willing to make investments to reduce smells, but there is no guarantee that the plant will ever be odor-free.

Staff Writer Randy Billings can be contacted at 791-6346 or at:

Twitter: @randybillings


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