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That mid-summer odor that sometimes hangs over the eastern part of Grand Marais may be dissipating. This is because Grand Marais PUC is looking at purchasing a Packaged Biosolids Odor Control System (BOCS) that captures and neutralizes odor-causing compounds for the North Sludge Holding Tanks at the wastewater treatment plant.
The BOCS would capture and treat off-gassing from the North Sludge Storage Tanks.
A facility plan completed in 2016-2017 outlined steps the city could take to reduce the odor. However, the project also dealt with effluent permitting related to mercury and was postponed until decisions about when the mercury limit would be made.
Since then, there have been numerous complaints about odors emitting from the wastewater treatment plant during the busiest part of the year. Steps have been taken to lessen the smell, but more needs to be done.
Scott Schaefer, PE, speaking remotely, presented a technical memorandum draft of the wastewater treatment plant to the PUC at the commission’s January meeting.
As the sole wastewater treatment facility for the county, the plant is a busy place. All told, The plant treats wastes from four primary sources: Grand Marais business and citizens; Voyageur Brewing (typically, brewery wastewater has highly variable concentrations throughout the brewing/cleaning process but overall is significantly 2 higher strength than general municipal wastewater); Septic system services (i.e., G&G) discharges slug loadings, municipal characteristics, (the community places high value on this service), and the city accepts leachate pond water from the former west end taconite plant, which may contain additional contaminates.
In his report, Schaefer pointed out that the odors generated are likely “due to a lack of oxidation and stabilization of the mixed liquor solids. Typically, oxidation ditches provide high volume-to-load ratios and high solids inventory, allowing for stabilization of the solids to occur within the oxidation ditch, bud due to the oxidation ditch being overloaded, a lack of stabilization occurs before the solids are wasted to the Biosolids Storage Tank.”
Schaefer presented several options and the costs of those options to the PUC. The Odor Control System cost estimate is $292,000 to $375,000. Replacing WAS piping at the plant would run from $40,000 to $55,000; Blower piping improvements run $140,000 to $175,000; an aerator upgrade would cost between $750,000 to $950,000, and an additional aerator would cost $600,000 to $800,000. All of the costs included engineering, materials, labor, etc.
Next, Schaefer presented an implementation strategy. He suggested the city purchase the Odor Control System for the sludge holding tanks, defer buying the WAS piping, and defer Blower Piping improvements but purchase the aerator upgrade for the oxidation ditch aeration.
PUC board member Charles Hathaway asked City Administrator Mike Roth how the improvements would be paid for, and Roth explained the city could pay for some of the work through general funds and through raising rates. Hathaway asked if the city could bond for payments and Roth said it wasn’t likely, but he would look into it. Other funds can be sought as well.
Both Hathaway and PUC member Craig Schulte voiced support for the plan, and Schaefer will work with Roth to come up with a timeline and cost of the project. However, noted Roth, “This isn’t a silver bullet. I guarantee it (the plant) will smell again.”
Next, the PUC approved the purchase of a new pump for a lift station right behind city hall. City workers replaced one of two pumps in the downtown lift station, pulled the other old pump, and sent it in for repair. Refurbishing the more than 25-year-old pump came in at $21,000. The cost to buy a new pump and have it shipped and installed is $28,300. Commissioners okayed the purchase of a new pump which will take 10-12 weeks to arrive. Once it is installed, the expectation is that the lift station will be “nearly trouble-free for a long time in the future.”
Special utility rates
Shane Steele, the Sustainability Coordinator, presented three special rates for utility customers, Off-Peak, Dual-Fuel, and Residential EV Charging. Here is a thumbnail sketch of these programs. For more information, go to the Grand Marais City homepage and look under the PUC for more details.
City residents with an electric heating system that stores electric heat (in-floor boiler heating, heated brick storage) may qualify for an off-peak electric heat discount. That depends, though, if the customer provides PUC with an appropriately sized meter socket installed at a location mutually agreeable to the customer and Grand Marais PUC.
Grand Marais customers who have an electric heating system combined with an established alternative heating source (fuel oil, natural gas, propane) may qualify for the Duel-Fuel Electric Heat Discount. In addition, a load management receiver must be installed by the Grand Marais PUC for the utility to remotely control the electric heating system during control periods.
Folks who own an electric vehicle charging home system may qualify for a discount rate. The customer must provide an appropriately sized meter socket installed at a location agreeable to the PUC and customer.
Finally, if you don’t own a renewable energy source but want to participate, you can purchase Renewable Energy Certificates through the SMMMPA Green Power Purchasing program. Grand Marais PUC purchases renewable energy certificates from SMMMPA. In 2023 SMMMPA will increase the REC rate from renewable energy.
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