City of Bloomington prepares for a new PAC System

Image Courtesy of Illinois State University 

NORMAL, Ill. – The City of Bloomington has had issues with its water supply since January of last year.

Assistant Water Director Brett Lueschen and Water Purification Superintendent Scott Joyce explain why this is happening.

“We’ve noticed in the last few years that maybe the levels of the taste and odor compounds, MIB and geosmin specifically, are higher than they were in the past,” Joyce said.

After the drought in the late 80s, Joyce explained how filters were changed from anthracite to a GAC, which is a similar product to PAC, a granular active carbon, to correct the water’s odor and smell.

“In the filters, we’ve got the GAC, and that was supposed to be the primary taste and odor solution going forward,” Joyce said. “They still were using a little bit of the PAC at the time, but not like we’re dosing now. It’s not working as well as we would like, which is why we pursued the PAC to do a lot of the heavy lifting.”

Joyce also touched on how the levels of the lakes can correlate with the number of algae blooms or MIB levels in the water. He explained that when the lake level drops, less water is cycled through, which allows MIB and algae to become more prominent.

“If the water is below the spillway, you’re dealing with a fixed amount of water, and that’s when we see the algae blooms accelerate or potentially cause a little higher level in the MIB,” Joyce said. “The lower the lake, the higher the taste and odor. That’s something that we’re going to look into going forward.”

Since the concerns in January of last year, Joyce mentioned some efforts that have been made to fix the odor and smell in the water, like lowering the threshold of chemicals that can be tasted to 10 nanograms per liter.

“Throughout this early spring and summer, we were able to bring the taste and odor compounds down to a level that is below the threshold,” Joyce said. “The threshold is around 10 nanograms per liter…we have done that since early summer.”

Another effort to reduce the smell and odor involved using a pump to create a temporary PAC system.

“Scott and staff up at the water treatment plant took a tank and a pump that we no longer use for another dose of a chemical, and took that equipment and turned it into a temporary PAC system with the approval of the EPA,” Joyce said.

When it comes to switching the water supply as a whole, Joyce said that switching the water supply from lake to lake could take as little as 15 minutes.

“Two direct sources are Lake Evergreen and Lake Bloomington,” Lueschen said. “We can actually also pull water out of the Mackinac River, which just pushes the water from the Mackinac River into Lake Evergreen.” 

Moving forward, Lueschen said that a new PAC system will be implemented starting in low doses this winter to overall improve the quality of Bloomington’s water.

“When we start seeing it, we may end up dosing PAC powder activated carbon all the time at a very low dose,” Joyce said. “When Scott sees these numbers starting to rise in the reservoirs, he could actually start dialing that PAC up, and hopefully, we won’t have another taste and odor outbreak like we have in the past. We have that new PAC system that’s coming here this winter.”

Joyce mentioned how MIB and geosmin are not regulated chemicals that make the water unsafe to drink, and that their goal is to provide safe water to all of their customers.

“Our water always meets regulations,” Joyce said. “That’s one thing that we take very highly. Our water has always, even when we did have those high tastes and odors, tested good. We’ve never had to worry about an issue of not providing good water.”

The City of Bloomington is set to get a new PAC system this winter to improve the water quality.