LEWISTON — Bids for a methane-burning electricity generator and solid waste digester at the Lincoln Street headquarters of the Lewiston-Auburn Water Pollution Control Authority should start coming in next week.
Superintendent Mac Richardson said he expects the winning construction bid for the project to be announced at the end of July.
Richardson said a mandatory bidders' meeting is scheduled for June 30. Final bids are due back to the authority by July 14.
The new facility's job will be to reduce the amount of solids the water treatment plant has to deal with. It does that by using anaerobic micro-organisms and heat to digest the solid materials left behind by sewage treatment. Right now, those materials are composted, used to fertilize farms and sent to landfills.
"Once we clean the water, we have to deal with all the stuff we remove and that can be expensive," Richardson said. The digestion process is expected to reduce the amount of solids by as much as 40 percent.
"A second happy byproduct of digestion is that it produces a methane-rich gas," he said. "Once it's cleaned, it is essentially very high quality and can be burned."
Richardson said the authority plans to burn the methane in two newly constructed generating engines.
All told, he hopes the facility will generate about 150 kilowatts of electricity per month, enough to cover a portion of the facility's electrical use, and save about $15,000 to $20,000 per month.
"Down the road, we feel that there are other materials, that could be good candidates for this kind of digestion treatment," Richardson said. Those could include grease and oils and airplane de-icing treatments.
"If we can start to treat those high-energy materials as well, we might be able to be even more energy-independent," Richardson said. "The wonderful thing about this project is that every time we turn around, we find another benefit."