Understanding the ultrafiltration process

Cutting-edge technology brings safe water to the city.

Our ultrafiltration water plant, located in Columbia Heights, is a state-of-the-art facility. This water purification method allows us to prepare up to 70 million gallons of Mississippi River water per day for drinking. The filters remove particles so small that a standard microscope can’t detect them.


The City’s new Ultrafiltration Plant at Columbia Heights uses state-of-the-art technology to provide safe water to Minneapolis. 

A lot of water from some tiny fibers

The ultrafiltration process uses hollow fibers to take particles out of the water. The fibers are porous, letting water through and keeping the particles behind. The fibers are tiny but there are a lot of them. There are about 43,008,000 fibers cleaning the city’s water. The fibers combined create a surface area of 1,669,000 square feet. If put end-to-end, these fibers would stretch more than 40,000 miles, or about 1.6 times the earth’s circumference at the equator.

Impurities as small as 0.03 micrometer (µm) are filtered out of the water you drink. The thickness of a U.S. dollar bill, red blood cells, and tobacco smoke are larger than the tiny holes in the fibers. Ultrafiltration removes nearly all viruses from the water; however, a fraction of them cannot be completely removed. Any threats posed by the pathogens left behind are mitigated by chlorine treatment. 

Dissolved salts and minerals add to the good taste of our water and are small enough to to not be filtered out of the water. The natural minerals in the water also improve water quality by making the water stable and preventing pipe corrosion.

One of 40 high-tech fiber filtration units at the new Columbia Heights Ultrafiltration Plant

The Ultrafiltration Plant will remove particles as small as 0.03 micrometers (µm)


A cross section of an ultrafiltration module shows the thousands of hollow fibers packed inside. 


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