MONROE — Operations to ensure the city will never again be plagued by odor from the wastewater treatment plant are already underway, Utilities Supervisor Mike Kennison said Thursday. 

“By spring it should be ready to go,” Kennison said. 

Currently, the system is in place and workers are attempting to humidify the bacteria despite cold weather. 

The plan to mitigate odor problems that have driven complaints since the wastewater treatment plant was first built over five years ago came together in late 2017. Kennison approached members of the Monroe Common Council, along with Timothy Bronn, senior vice president of McMahon Associates Inc. of Machesney Park, Illinois, with a plan. 

Kennison said the cause for the smell was the result of a constantly running equalization tank, which was part of the $25 million project to create the now updated treatment plant for the city. He added that the plant’s designer, AECom, should have known the smell would occur and could have taken steps during the process to avoid the problem but did not. 

Instead, the city approved a plan for a biofilter system at the recommendation of two different options by Bronn.

A biofilter system utilizes the growth of bacteria on natural components. In Monroe’s case, it is shredded tree roots, or wood chips. The bacteria use sulfur as an energy source in the oxidization, nullifying the odor caused by hydrogen sulfide, which Bronn said is a common gas at treatment plants like the one in the city. Though Bronn noted the upfront capital expense of an estimated nearly $488,000 was the most expensive option initially, the maintenance costs are the lowest at $194,000, making it roughly $115,000 less costly than the other two options.

A recent change order request by McMahon shifted the total project contract cost from $562,000 to over $569,000, which was approved by council members at their meeting Feb. 4. The shift in work included nearly $6,000 for work to stabilize the ground where a foundation for wood chip storage was poured and nearly $2,000 for added heat trace circuits and an outdoor LED light pole.

Everything is in place, Kennison said, with the exception of $60,000 to be paid on the contract and the return of workers one last time to address small touch ups. Little maintenance will be required for the system, he said, with the exception of wood chip replacement that occurs roughly every seven years. 

Kennison said he looks forward to the odor no longer being an issue and for the city to no longer receive complaints from city residents who have been dealing with it for years.