Big upgrades loom for Middlebury sewer plant

MIDDLEBURY — A consultant is helping the town of Middlebury plan for what could be a multi-million-dollar upgrade to its 18-year-old wastewater treatment plant. It’s all part of 20-year review that the state of Vermont requires of all municipal wastewater facilities.
Middlebury’s current treatment plant is located at 243 Industrial Ave. It replaced the former plant off Seymour Street, which now hosts a pumping station and the Middlebury police headquarters. The new facility was equipped with some of the best technology of the day, allowing it to process sewage sludge and handle considerable waste flow from homes, business and some of the town’s top industries — including Agri-Mark/Cabot, Vermont Hard Cider, Otter Creek Brewing and Aqua ViTea.
Bob Wells, Middlebury’s wastewater superintendent, explained the wastewater equipment is being worked hard, much of it around the clock. This has led to some equipment wearing out, and the technology is advancing to a point where replacement parts for older systems are becoming scarce.
“We’ve had a drum go on one of our belt presses, we’ve had some heaters go and we’ve seen flights wearing down to a point where the whole flight mechanism will have to be replaced,” Wells said. “We’re talking large expenditures.”
The flight mechanism helps remove grit in the wastewater treatment process.
Middlebury’s wastewater facility is classified as an “activated sludge treatment plant” that uses sequencing batch reactors to biologically treat the waste and remove phosphorus content. The facility then uses ultraviolet technology to disinfect the effluent prior to discharging it into the Otter Creek in accordance with state and federal permits.
While the state won’t prescribe upgrades to Middlebury’s plant until 2020, Wells and other town officials want to be proactive in defining the project well in advance. Helping the community through this process will be the Burlington-based company Tata & Howard. Its engineers are scrutinizing Middlebury’s entire wastewater treatment process, and will point out potential areas of improvement. They issued a preliminary report on their progress earlier this month.
“We’ve a good handle on what’s going on and what needs to be replaced, so we thought it would be a good idea to start the evaluation study at this point,” Wells said.
MIDDLEBURY WASTEWATER TREATMENT Plant Superintendent Bob Wells talks during an open house tour last August about how the facility separates solid waste from water. He said the facility produces about 4,900 tons of wet waste annually; all of it ends up fertilizing soy fields at the Adams Farm in Panton.
Independent file photo/Trent Campbell
It’s not all about repairs and improvements; it’s also about future economic development opportunities for Middlebury.
Local officials want to make sure the wastewater plant maintains enough reserve capacity to not only accommodate current clients who might grow their families and businesses, but also any new, major industries that might settle in Addison County’s shire town during the coming years.
The “organic load capacity” of the plant is measured in pounds of BOD (Biological Oxygen Demand). The plant was designed in 2000 for an influent BOD loading of 8,802 pounds, and the facility has been running at around 63 percent of that capacity based on a five-year average, according to the Tata & Howard preliminary engineering report.
“We still have some organic load to allocate to industries, but it’s getting smaller,” Wells said. “We want to make sure we’re ahead of the game, so that if there’s another industry that comes into town, we’re going to be able to assist them,” Wells said.
How can that be done? Here are some facility improvements that wastewater staff and engineers have been floating:
•  A primary clarifier, which would remove around 30-40 percent of the organic load coming into the process. So a clarifier would allow the Middlebury plant to allocate 12,000 pounds of BOD instead of the current 8,802.
•  An anaerobic digester, which — like Green Mountain Power’s “Cow Power” program — would manufacture energy from waste while at the same time creating a fertilizer byproduct.
•  A more efficient de-watering process for the waste that enters the facility.
“I expect the whole process to be changed out for the bio-solids,” Wells said. “It will be a different type of de-watering, compared to the current process involving a belt-filter press.”
Once municipal and state officials agree on the scope of needed improvements, they can then determine a final price tag and how the upgrades will be financed. Wells said the costs could be paid through a bond, increases in wastewater fees, or a combination of both. But he stressed Middlebury could be in line for some grant money to defray some of the costs.
And there’s some good news coming on the bond front. Wells noted the original bond that voters OK’d almost two decades ago is slated to sunset in 2022. So officials could schedule a new repair bond to immediately follow retirement of the current one, so taxpayers wouldn’t feel the pain for paying off the two large debts simultaneously.
“We have a long time before that happens, and right now we have a preliminary report we’re reviewing,” he said.
Middlebury’s Infrastructure Committee will participate in that review.
Wells said it’s impossible to even ballpark the cost of upgrades the wastewater plant will need, but he said it will likely be in the “millions.”
Reporter John Flowers is at [email protected].

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