A year after the Missoula City-County Health Department issued a "notice of violation" to both Missoula's Wastewater Treatment Plant and neighboring EKO Compost because their incessant stench constituted an "ongoing public nuisance," the $76,000 study intended to identify the origins of the odors has been released.
"There are no big surprises," says Starr Sullivan, superintendent of the treatment plant. "They found that the odors were half us and half EKO Compost."
The conclusions of the Odor Characterization Study, conducted in part by Bob Bowker, an internationally renowned odor control expert, were presented to Missoula City Council's Public Works Committee last week. The study shows the treatment plant is responsible for 53 percent, and EKO Compost 47 percent, of the odors that for years have been the bane of residents who live downwind of the sites on the corner of Mullan Road and Reserve Street.
Both facilities received a list of corrective actions. In the short term, the treatment plant will, in part, mitigate for odors from its thickened waste activated sludge tank and seal manhole covers. EKO Compost will reduce its pre-mix piles that contain sewage and other composting materials, among other steps.
In the long term, the treatment plant will replace by 2012—as has been planned—its "headworks," where all of Missoula's raw sewage comes in. EKO Compost will develop a new operations and maintenance plan to be approved by the Montana Department of Environmental Quality. EKO will also develop an improved biofilter design to treat the exhaust from the aerobic compost piles.
"We've already incorporated part of the study and we're already seeing results from it," says EKO Compost manager Terry Munnerlyn.
Was it worth the $76,000?
"I think it was," Sullivan says. "The study really qualified it and quantified it. It really pinned it down to the exact causes, the exact sources, where most of the odors are coming from. So I think the study was important for that, just to confirm our suspicions. You don't want to spend a lot of money on a suspicion or a guess."