Ice buildup in Rochester’s potable water storage tanks used to be a common problem during Min- nesota’s prolonged winters. The ice chipped away
at paint on the interior walls, causing extra maintenance
and budget concerns for Cary Johnson, water operations manager for Rochester Public Utilities (RPU).
It was a problem that could only increase. Home to
the Mayo Clinic, Rochester is a fast-growing community: the utility receives about 600 new accounts a year.
Currently about 20 water storage tanks with a combined capacity of 16. 5 million gallons serve a population of 112,000.
Until a few years ago, John-
son and RPU dealt with the
problem of ice buildup in their
reservoirs the same way utili-
ties in many other northern
and cold-climate towns do: by
exercising the tanks. In theory,
Searching for a better alternative than exercising the
tanks, Johnson learned that GridBee® GS submersible
electric mixers from Medora Corporation (Dickinson,
N.D.) might provide a cost-saving solution. The mixer
deploys on the bottom of the tank and creates a constant
foor-to-surface fow ensuring new incoming water is
properly mixed throughout the water column. New wa-
ter contains essential BTUs (heat) which is then actively
mixed throughout the entire tank, keeping ice at bay and
water temperature and water age as uniform as possible.
Johnson installed the frst mixer in one of the larger
reservoirs. “We experienced virtually no ice buildup
in the Bandel Reservoir after installing the mixer,” he
said. Since then, Johnson has added mixers to most of
the existing tanks and as new tanks go online. Since
ice damage is no longer the problem it once was, their
interior tank painting schedule has extended by three
years or more.
The mixers provide benefts year-around as well.
They ensure uniform distribution of disinfectant, minimize thermal stratifcation and prevent short-circuiting
and stagnant water conditions. Their unique circulation
pattern washes across the foor and sides of the entire
tank where bioflms are most likely to accumulate. This
circulation constantly replaces benefcial disinfectant,
killing the bacteria in the most critical parts of the tank.
“The mixers make my job easier and give me peace
of mind,” said Johnson. “We had to stay on top of exercising the tanks, and that’s not an issue any longer.”
And extending the painting schedules is a relief for the
utility’s budget. WW
To learn more about Medora Corporation or GridBee® GS submersible
electric mixers, visit www.medoraco.com.
Active Mixers Bring
Peace of Mind to
Submersible tank mixer solves ice
problem in potable water storage tanks
and provides year-round benefts.
GridBee® GS- 12 submersible tank mixers provide municipalities with a low-cost solution for meeting water quality
standards and preventing ice damage.
Cary Johnson, water operations manager, Rochester Public
GridBee mixers helped solve the ice buildup problem in Rochester’s water storage tanks.
Presented by Medora Corporation