As recently as 1962, Missoula dumped millions of gallons of untreated sewage into the Clark Fork River each day. It was common protocol among the nation’s cities until federal regulations put an end to the practice.
Nearly 60 years later, Missoula’s use of wastewater and other biosolids has transformed the city into a national leader when it comes to managing waste and directing it toward secondary, beneficial uses.
That includes diverting nutrient rich water to grow 160 acres of hybrid poplar trees for wood production, and directing biosolids from the treatment facility, along with green waste, to an adjoining composting facility.
The plant also captures biogass to generate 25 percent of its own electricity.
“I’ve seen it down to 22 or 23 percent, but I’ve also seen it up to 34 percent,” said plant manager Gene Connell. “It will grow slowly over time as the city grows and the organic flows coming into the plant grows, creating greater gas production.”
Connell led members of the Missoula City Council and other department heads on a facility tour Wednesday to showcase the plant’s efforts to cut the city’s carbon footprint, itself a stated community goal.
While the wastewater tanks churned and the motors hummed, a grove of poplar trees nearly a decade old capped the horizon, their leaves golden in the afternoon sun. Within the coming years, the first rotation will be ready for harvest as saw logs.
The trees are watered with treated discharge from the plant.
“We’ve been diverting 1 million gallons a day of discharge from the Clark Fork River during the summer months,” Connell said. “Starting next year, we’ll be able to diver 1.5 millions of gallons a day.”
Directing water from the plant to the poplar grove diverts nutrients that otherwise would end up in the Clark Fork River. While the water has been treated, it still contains trace amounts of phosphorous and nitrogen.
And that, Connell said, causes algae blooms, which degrade aquatic habitat.
“It diverts the nutrients that would be in that wastewater out of the river, and it puts it to a beneficial use growing trees,” said Connell. “We’re able to divert that out and that helps the Clark Fork River.”
Waste generated from the city’s residents undergoes a complex series of processes, including ultraviolet light and bacterial treatment. The process is highly advanced and has come a long ways since Connell began working at the plant 27 years ago.
But no process is perfect, he said, and for that, the city’s composting facility comes into play.
“The compost operation was a private company making compost since the mid 1970s, but the owner retired so the city took the opportunity to purchase it,” Connell said. “That facility is very valuable for us for the disposal of municipal biosolids.”
Organic remnants in the wastewater treatment process, along with 50,000 cubic yards of green waste, such as leaves, are process together to create a valuable soil amendment, which in turn generates revenue for the city when sold to the commercial market.
While the city could simply dispose the waste at the landfill, doing so consumes precious space, along with an otherwise valuable resource.
“Both of those waste products are put together to make a valuable product that can be marketed and create a revenue stream,” Connell said. “The largest single market is mining reclamation. Landscapers use the next largest amount, and after that it’s the truck loads going to people’s gardens and farms.”
Last week, the city unveiled plans to rid itself off fossil fuels and replace it with 100 percent clean electricity by 2035. City Leaders have also signed a plan to keep Missoula committed to the goals of the Paris Climate Agreement, despite the federal government’s threats to do the opposite.
The city also has signed on in support of the EPA’s Clean Power Plan, and in July, it adopted a Zero by Fifty blueprint, setting a goal to cut municipal waste to zero by 205o.
City Council member Jordan Hess sees the municipal wastewater plant and its novel operation as a key player in those ambitious goals.
“Everything that’s going on out here is innovative, but there’s a payoff as well,” Hess said. “We’re not buying as much electricity commercially because we’re producing it on site, and we’re taking what would be a greenhouse gas and capturing it and using it for a benefit. It’s all about thinking of waste streams differently and minimizing our impact.”