82% less chlorophyll-a in the City of Minneapolis


Applied to control algal blooms

Potable water

Source to the city's 500,000 citizens


Chlorophyll-a reduction achieved

Clean drinking water with ultrasound technology

In City of Minneapolis, Minnesota, US – The Mississippi River is the only source of drinking water for half a million residents. Each year, the Water Treatment & Distribution Service (WTDS) pumps approximately 21 billion gallons of water from the river.

The extracted water goes through multiple treatment processes before it is safe for human consumption. Therefore, ensuring the highest level of water quality is crucial for WTDS.

Committed to green solutions

Devoted to both its consumers and the environment, WTDS continuously chooses holistic approaches in its water treatment processes. These include softening, sedimentation, filtration, and disinfection.

The treatment starts with collecting water from the Mississippi River and applying lime softening. It continues with the removal of unpleasant taste and odors. Additionally, organic material is reduced.

Ultrasound against cyanobacteria

Next, the water is stored in a reservoir that supplies water for the Columbia Membrane Plant. Being uncovered, the reservoir allows for a steady inflow of nutrients and algae from the river. Consequently, this creates the perfect conditions for algae to grow.

WTDS’ greatest concern was that algae would clog membranes in the filtration plant. The Department of Public Works is on a constant lookout for toxic algae that could potentially affect the taste and smell of water.

As of July 2019, the City of Minneapolis uses LG Sonic technology to reduce filamentous cyanobacteria and flagellate green algae.

Pure water despite extreme weather

Since the installation of the LG Sonic technology, the reservoir remained free of algal blooms, despite exceedingly high summer temperatures. Phycocyanin levels never exceeded 2 μg/L, and Nephelometric Turbidity Units (NTU) remained on average at 2.5, even during heavy rainfalls.

LG Sonic technology became an important tool for delivering the highest water quality. The City of Minneapolis takes pride in removing impurities more effectively than the federal drinking water standards require.

LG Sonic’s ultrasonic technology is an integral part of Minneapolis’ water treatment process. The company is always prompted to respond to technical questions. Minneapolis also considers the unit’s online instrumentation to be priceless.

Matthew Sullivan – Lab Supervisor, City of Minneapolis – Department of Public Works

Division of Water Treatment & Distribution Services

Project details

Location Minnesota, US Industry Drinking water Client City of Minneapolis
  • 82% reduction in chlorophyll-a
  • 70% reduction in phycocyanin
  • NTU remains below 2.5 even during heavy rainfalls
  • No algal blooms despite hot summer weather
In City of Minneapolis, Minnesota, US, the Mississippi River is the only source of drinking water for 500,000 residents. The Water Treatment & Distribution Service (WTDS) of the City pumps approximately 21 billion gallons of water from the river.

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Applied product

LG Sonic developed the MPC-Buoy specifically for larger water surfaces such as cooling reservoirs and drinking water reservoirs.


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