WORTHINGTON — Meeting via conference call Monday afternoon, the Worthington Public Utilities Water & Light Commission approved a series of actions related to potential construction of a new municipal wastewater treatment facility.
Worthington’s existing wastewater treatment plant north of town was originally built in 1962. It has been upgraded three times since then, the most extensive of which was in 1989.
Kris Swanson, principal engineer with Bolton & Menk, began working with WPU in 2016 on an asset inventory and evaluation of the water treatment plant. At the time, Swanson said aging equipment was noted, including tanks that needed to be replaced within the next three to 10 years.
That same year, the city’s permit — issued by the Minnesota Pollution Control Agency — expired. The permits are typically issued every five years.
Now, with the infrastructure needs growing more apparent, Swanson said the MPCA has said it will begin work on the city’s permit this spring and summer.
Swanson said the city has essentially two options — to replace what is currently in place (at a cost of $15 million); or to build a new wastewater treatment facility with technology more suited for the future (estimated at $20 million). Property has been identified either north or east of the existing site for new construction, and there are grants and low-interest loans the city can apply for to help fund the project.
The existing facility treats wastewater through a three-stage trickling filter. After sand, gravel and garbage are removed from the wastewater, the heavy solids settle out and trickling filters (bacteria on rocks) eat the remaining waste before the liquid is discharged into a receiving stream.
“These trickling facilities do a great job, but what they’re kind of deficient in is nutrient removal — ammonia, nitrogen, phosphorus — some of these things that cause rivers to turn green and hypoxia zones in the Gulf of Mexico,” Swanson explained. “These nutrients have really become the driving force of the Minnesota Pollution Control Agency and water cleanup over the last 20 or 30 years.”
If WPU were to consider a new facility, Swanson encourages the construction of an activated sludge plant, which would remove the nutrients and “is really built for the future.”
Worthington’s industrial wastewater facility already has an activated sludge plant in place, he said, noting it removes ammonia, nitrogen, phosphorus, Biochemical Oxygen Demand (BOD) and suspended solids for a very clean effluent.
Swanson said there’s been a trend over the past 30 to 40 years to replace trickling filters with an activated sludge plant. He also noted that it’s a four- to five-year process to get a facility designed, built and operational.
“We still have additional time that we need to make the existing infrastructure last,” he added.
Among the actions taken by commissioners Monday were resolving to accept the wastewater facility plan, setting a public hearing for 2:30 p.m. May 18, and authorizing WPU staff to accept the proposal from Bolton & Menk to conduct preliminary engineering work.
In other business, the commission:
Received an update from WPU General Manager Scott Hain on the potential conversion to biological treatment of water. In gathering some of the data requested by WSB, the firm that conducted a feasibility study for the project, Hain said dissolved oxygen levels are at higher than expected levels, which could lead to significant cost savings if the project moves forward.
“The way we’re moving water could be providing enough oxygen so we wouldn’t need the expense of installing blowers for aeration,” Hain said.
A preliminary study review is slated for June 22, with the study potentially completed by mid-July. After that, Hain said WSB would be invited to a commission meeting to present its findings.
“We anticipate that if we make the decision to move to biological treatment of our water, it could yield very significant savings,” Hain said.
Was notified of discussions taking place with JBS about the potential for a large electrical expansion being discussed by the local pork processing facility. Hain said the plans could lead to either significant expansion of the city’s east electrical substation, or the construction of a new substation near JBS.
“We’ve got cost estimates on expansion, but not yet on a new substation,” Hain reported. “In order for us to expand (the east substation), we would need additional property.”
With Monday’s announcement by JBS that it was closing indefinitely due to COVID-19, Hain said the discussions may be delayed for now.
Learned of the steps being taken by WPU staff to maintain social distancing and serve the public during the COVID-19 pandemic. Customer service hours at the WPU office have been reduced to 12:30 to 4:30 p.m. Monday through Friday, and Hain said that may be reevaluated as the number of positive cases rises in the community.