Bloomington's tap water tastes bad again. Here's why and what you can do.

It’s that time of year again: Bloomington’s tap water has begun to take on an earthy, musty taste. Or as a Redditor described it, “It’s fishtank season.”

The city’s water quality coordinator emphasized that despite the foul odor/taste, the water is safe to drink and meets all federal and state drinking water standards.

Here’s why the water, for several years in a row, has taken on a musty taste in late summer/early fall.

Why does the water in Monroe County taste bad?

Utility staff believe the culprits of the bad taste are two compounds produced by algae: methylisoborneal (MIB) and geosmin.

Justin Meschter, the Bloomington utility’s water quality coordinator, said tests detect higher concentrations of the compound usually after an extended period of hot, dry, sunny days.

The conditions make foul-tasting water more likely for two reasons:

• They promote algae growth and therefore increase concentrations of MIB and geosmin.

• They lower the water table on Lake Monroe, the county’s drinking water source, which means City of Bloomington Utilities may be drawing the water from different water columns that contain more or different types of algae.

Meschter said the utility has not pinpointed which algae are to blame, though staff suspect blue-green algae, in part because other utilities that have reported similar problems have identified that type of algae as the culprit.

When will Bloomington's foul water taste go away?

Meschter said the CBU cannot predict when the bad taste appears or goes away, as it depends in part on weather. Last year, for example, the problem began in early September and lasted a little more than two weeks, but concentrations of the offending compounds then also were higher than they are this year.

The utility this year is testing the water for the compounds twice a week, up from once a week in prior years, but Meschter said it’s still difficult to determine how much rain and/or how much of a temperature drop is needed for the bad taste to dissipate.

What is Bloomington doing to mitigate/prevent the foul tasting water?

Meschter said CBU has been doing lab experiments on changing the types and compositions of the carbons and other compounds it uses to counteract the levels of MIB and geosmin, but he said the process is tricky because the utility has to keep in mind how the changes affect other aspects of the treatment process.

Ideally, the utility could add a carbon contact chamber — essentially a large water pitcher filter — that would reduce the concentrations of the compounds that are causing the problem, Mischter said. However, he said it’s difficult to put such a chamber into the system retroactively, and it likely would be costly for ratepayers.

Until such a fix is in place, Mischter suggested people use pitcher filters or the filters that come with their refrigerators. Some people also fill a pitcher with water and add fruit wedges, which help, at least somewhat, with covering up the foul taste.

A poster on Reddit suggested another solution: “Adding a little lemon juice year round is my remedy.”

Boris Ladwig can be reached at bladwig@heraldt.com.

This article originally appeared on The Herald-Times: Monroe County's water tastes bad again. Here's why, what you can do.