ATWATER — A small lake once popular for swimming and fishing is now the site of an experimental project aimed at reviving local recreation.
Nanobubble technology is currently being used to oxygenate the waters of Lake Taddo in Atwater, Minnesota, about 85 miles west of the Twin Cities.
Officials from the Middle Fork Crow River Watershed District and representatives from Morea, the Los Angeles, California-based company that owns the technology, started up the system on July 3. The system is expected to operate for about three months as a pilot project to demonstrate the technology’s ability to reverse eutrophication that has made many lakes unsuitable for recreation.
“This could be a turning point for the region,” said Dan Coughlin, district administrator for the Middle Fork Crow River Watershed District, who hopes the demonstration on the 10-acre lake will dispel any skepticism about nanobubble technology.
The watershed district is working with the city of New London to secure funding to install a larger nanobubble system at the community’s mill pond.
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For decades, Mill Pond has been a source of foul-smelling hydrogen sulfide emissions every spring when the ice melts. This is caused by a lack of oxygen in the water beneath the winter ice and a century of phosphorus and other nutrients that have built up in the sediments. Bacteria consume nutrients in the absence of oxygen, producing the harmful gas.
So-called cultural eutrophication – the rapid buildup of nutrient-rich sediments due to human land use and activities – has also proven to be a plague on Lake Tad, turning the lake bottom into soft mud and filling the water with pea-soup-like algae and a thick layer of aquatic plants.
Before the nanobubble system was installed, the watershed district contracted with Lakes Aquatic Weed Removal of Orr, Minn., to remove as much aquatic vegetation from the lake as possible using an “underwater lawnmower.” Reducing the lake’s organic load before starting the nanobubble system will help the system get started faster, Coughlin explained.
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The owners of Lakes Aquatic Weed Removal spent more than two days removing more than 40 truckloads of biomass, despite local flooding preventing some of their staff from helping with the work.
The best is yet to come. Minnesota native and global sales director for Morea, Chris Stephens, said Atwater residents should see the lake’s water quality improve day by day over the coming summer.
While it’s still a pilot project here, Stephan said the company’s technology is literally proven all over the world: the company has more than 1,000 installations in 55 countries.
The system includes a large water pump, an oxygen concentrator, and the company’s patented nanobubble generator. Oxygen is pumped into water drawn from Lake Tudor and then the water is passed through the nanobubble generator’s diffuser, which separates the nanobubbles as the water passes through.
Water enriched with oxygen and nanobubbles is pumped into the lake at a rate of 1,000 gallons per minute. The nanobubbles are tiny, about the size of a virus, and have no buoyancy, which Stephens says allows oxygen to permeate evenly throughout the water column, including at the bottom.
This is very important because standard aeration systems do not allow the bubbles to rise to the surface so quickly that they can cover the sediments at the bottom with oxygen.
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When the nanobubble system oxygenates the bottom, bacteria in the sediment start to eat the nutrients, which should harden the soft muddy bottom. Stephan says that this consumption of phosphorus will starve the algae, which will clean up the water overall.
While nanobubble technology has a wide range of industrial applications, Stephan says Morea has the only system that can be scaled up for use in bodies of water. “It’s the fastest growing system in our market,” he says. “We work with lakes like this all over the world.”
Watershed District program managers John Morales and Andy Johnson have been analyzing the system’s effectiveness and have made the project an outdoor laboratory by collecting and continuing to collect a variety of data on the lake’s water quality.
A small pond upstream from Tad Lake has monitors that record data on the state of the water in this management pond, and there are monitors in Tad Lake itself that are similarly monitoring any future changes.
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Coughlin is making the technique the focus of his master’s research. Put simply, he says it’s about “giving Mother Nature a chance to take a breather and restore natural balance.”
Stephens said it costs thousands of dollars a month in electricity to run the Tad Lake system.
If the technique proves effective, the bureau hopes it could be replicated in other watersheds in the region where excess nutrients are affecting water quality, such as Diamond Lake, where man-made eutrophication has led to algae problems.
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