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Boreal Community Media

Addressing Recent Waste Water Treatment Facility Odor

Jul 10, 2019 02:55PM ● By Editor

Media Release from the City of Grand Marais - July 10, 2019


The Grand Marais Wastewater treatment plant processes all of the waste that is flushed or drained to the Public Utilities sanitary sewer system within city limits. The plant recreates the ecological processes found in rivers to clean our wastewater before returning it to Lake Superior.

In the plant, wastewater cycles continuously through a round sedimentation tank. This constant flow helps break down and dissolve suspended solids moving through the structure while bacteria feed on dissolved solids to remove them from the water. As solids settle to the bottom of the sedimentation tank, staff transfer them to a sludge digestion tank. Bacteria in the digestion tank consume the solids, removing viruses and pathogens.

A certain level of unpleasant smell is inherent to a wastewater treatment facility. Recently, people in Grand Marais likely noticed that the wastewater treatment facility was emitting an unusually obnoxious odor. Temperature, humidity, precipitation, and the amount of incoming waste fluctuates continuously, significantly impacting the chemistry involved in processing wastewater. Generally, the more offensive odors coming from the plant stem from unbalanced ratios of waste, bacteria & oxygen in the sludge digestion tanks.

Typically a fraction of the solid waste in the facility’s digestion tanks is brought to Duluth for disposal one truck-load at a time in regular intervals.  This spring due to an upcoming construction project near the wastewater treatment facility that could impede truck access to the plant, Staff decided to empty the sludge digestion tanks entirely to make room for the excess sludge that would need to be stored until truck access was made available. As the digestion tanks began to refill staff had difficulty re-establishing an optimum balance of waste, bacteria & oxygen, and are taking steps to mitigate similar conditions in the future.

The Public Utilities Commission and Staff are mindful of the difficulty the odor presents to residents, business owners, and visitors. They currently pursuing changes to plant operations & investigating technological applications to reduce odor.

If you have any questions, please call Patrick Knight at 218-387-1848.

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