Bad Bloomington water taste not a threat to human health, possibly caused by algae, says CBU

“Our water tastes and smells like mold,” reads a complaint logged in the city’s uReport system on Sept. 15, 2021 by a city of Bloomington utilities (CBU) customer.

Reports like that have been coming in from all parts of the city, CBU communications manager Holly McLauchlin told the B Square on Tuesday.

McLauchlin said the bad taste and odor don’t pose a threat to human health or safety. That’s also part of the message in a news release that was issued by the city early Wednesday afternoon.

It’s possible that the bad taste and odor are caused by increased levels of algae in Lake Monroe, which is the source of Bloomington’s drinking water, McLauchlin said.

[Updated at 12:22 p.m. on Sept. 16, 2021: CBU has now confirmed the cause of bad taste and order is increased levels of algae in Lake Monroe.]

On Tuesday, McLauchlin told The B Square that CBU was investigating the cause of the bad taste and odor. One of several possibilities being explored was a potential problem with the mechanism used by CBU to add powdered activated carbon (PAC) to the city’s drinking water. It now appears unlikely that’s the cause.

PAC helps remove naturally-occurring compounds called Geosmin and Methyl-Isoborneol (MIB). But the reason CBU started adding PAC to the water was to help prevent the formation of disinfection by-products.

It was in 2017 when CBU started adding PAC to Bloomington’s water. According to the news release, “The current series of complaints is the first CBU has had since 2017.”

On Tuesday, McLauchlin told The B Square this year is the first time in a while that CBU has received this kind of taste and odor complaint—but that it was previously pretty common.

The past and possibly current seasonal routine for the bad taste and odor of Bloomington’s water in late summer and fall has been confirmed by several comments on social media outlets.

CBU’s leading theory attributes the current bad taste and odor to higher levels of algae in Lake Monroe.

That theory is consistent with Department of Natural Resources testing for algae, which in early September put Lake Monroe’s Paynetown and Fairfax SRA swim beaches on an “advisory alert” level. That’s the second of four alert levels—low risk, advisory, caution, closed.

Dry warm weather, like the Bloomington area has seen in the last few weeks, can cause higher levels of algae, and causes a spike in the organic compounds that algae produces, according to the city’s news release.

According to Wednesday’s news release, the filters used by CBU remove the algae itself, but the bad taste and odor caused by the algae-produced organic compounds persist after treatment.

The news release quotes CBU director Vic Kelson saying, “We are committed to transparency about the quality of the water we provide, which customers may access anytime at our website. We’re focused on identifying the cause of these unusual taste and odor issues to restore our customers’ usual good-tasting tap.”

The city maintains a dedicated webpage on water quality in addition to several datasets related to water quality.

The uReports filed about the taste of Bloomington’s water look like they start as early as Sept. 11.

That one reads [standardized capitalization and punctuation added]: “The drinking water coming out of our faucets has recently started tasting really bad. I tried putting it through a water filter and it is still undrinkable. I’ve lived in my home for six years and this is not a normal problem that we have. What could be causing this?”

Update from CBU at 12:22 p.m. on Sept. 16, 2021:

Water samples collected by the City of Bloomington Utilities (CBU) have returned results which confirm that increased lake algae is causing the taste and odor complaints. This is a system wide issue CBU customers are experiencing. The warm and dry weather this month has resulted in an increase in algae from Lake Monroe. The treatment process is able to filter all the algae itself, but the lingering taste and odor are very difficult to control in a conventional water treatment plant, and so at times they persist after treatment. This taste and odor, which has been described as “musty” “dirt-like” “moldy” “stale” etc. is not a health concern, but it is an aesthetic issue which is not uncommon for communities using lakes as their water source.

There are certain steps CBU is taking to try to eliminate the issue, such as increasing the amount of powdered activated carbon and copper sulfate added to the water to control algae and help with taste and odor issues. This is similar to using a filter at home and customers can use additional home filters if they still taste “lake”.
The taste and odor will continue for a while; it can take up to 7 days for water to get from the plant to the furthest customers and it will take time to build up enough powdered activated carbon/copper sulfate to improve taste and odor. CBU does not want to add more chemicals to drinking water than is absolutely necessary, so this is a slow and methodical process. Additionally, as the weather cools down the algae will return to normal levels.

CBU tests drinking water multiple times each day for many different quality parameters at sites across the distribution system and at the water treatment plant to ensure the water continues to be safe to drink.