What's causing it?

Last update: July 10, 2008 - 11:42 PM

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Source of tastes and odors

The source of the taste and odor problem is more specific than just an "increase in organic matter". Most T&O problems are caused by a few … read more specific compounds released by specific types of algae and other microorganisms. The two most common are "MIB" and geosmin. The threshold for tasting either of these is only about 10 parts per billion. It may be difficult to figure out the exact source. Sometimes a T&O problem originates in the water pipes, but given the widespread occurrence, this seems unlikely. It is more likely that the source is the river water (which supplies Minneapolis). More precisely, it is probably due to a "bloom" of a specific algae. This could be a phytoplankton (free-floating) algae, or it could possibly be a periphytic (attached) species living on rocks, probably in shallow water. Either way, it is probably caused by a specific species of blue-green algae (not all blue-greens cause T&O problems). T&O problems in lakes and reservoirs can sometimes be treated using copper sulfate or other chemicals, but this could be tough in a river (I would suggest taking a look at the impoundment behind Coon Rapids Dam though). More likely, the city will have to rely on adding powdered activated carbon over the short term, and perhaps granulated activated carbon over the long term (GAC filters would have to be installed - not cheap). Tracking the source of the problem could be helpful, even if it can't be treated, because it would be useful to be able to predict when the problem will occur, thereby reducing treatment costs - a lot! Meanwhile, households might try one of the filtration devices that contains activated carbon. This is a perennial problem in Phoenix, where we conducted research to find long-term solutions to solve it. Larry Baker, WaterThink LLC and the MN Water Resources Center.

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WHAT'S CAUSING IT?

An increase in organic matter, such as algae and decaying leaves, entered the drainage basin and has worked its way downstream the Mississippi River.

WHERE IS IT A PROBLEM?

Officials do not yet know the extent of the problem, but it could affect the entire Minneapolis service area, which includes: Minneapolis, Golden Valley, Crystal, New Hope, Columbia Heights, Hilltop, and portions of Bloomington and Edina as well as the Minneapolis/St. Paul Airport.

WHEN WILL IT BE FIXED?

There is no concrete timeline yet, but officials estimate about two weeks.

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