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Seasonal Taste & Odor

Seasonal Taste and Odor Due to Algae

Seasonal Algae Can Happen

Public Works completes ongoing testing on our water. At times typically during spring and fall, there may be taste and odor changes. This is caused by the presence of seasonal algae blooms in the raw water storage reservoir at the Catawba River Water Treatment Plant. The water does get treated after being in the raw water storage reservoir, but may retain the taste and odor change.

Water Quality 

The water is safe to drink. The earthy smell and taste are not a health risk, but one of aesthetic quality and common in water systems across the Southeast. Water quality tests performed throughout the water distribution system have confirmed that Union County water meets or exceeds all state and federal standards and remains safe to drink.

More Information on Algae

Algae naturally grows in water sources during warm weather. As it grows, it releases small compounds that cause a musty or earthy taste and odor. Although harmless, some individuals’ senses of taste and smell are extremely sensitive to them, even at low concentrations in drinking water. The compounds are detectable to people at different levels, but the standard threshold number is 5 parts per trillion. Some people may not notice any taste and odor until the levels are much higher. Others may never notice it.

Working to Mitigate

Public Works is implementing water treatment modifications to help mitigate the taste and odor. We will continue to monitor the situation and adjust processes as needed.

Strategies at Home

There are ways to help reduce the taste and odor at home. Consider chilling water and/or adding lemon. In addition, carbon filters- the type used in water pitchers or attached to faucets- may help.

We appreciate your patience as we continue to address this issue.

Frequently Asked Questions

What causes earthy taste and odor in tap water?

Algae naturally grows in water with sufficient nutrients, particularly when the combination of warm water and calm weather conditions exist. Two natural organic compounds are produced from algae- MIB (methylisoborneol) is produced during the algae's life cycle, and then when the algae dies off it releases geosmin. Although harmless, both MIB and geosmin cause an earthy taste and odor in the water, and both can be detected by people at very low concentrations.

Is earthy tasting and smelling water safe to drink?

Yes, the water is safe to consume and poses no health risks. The taste and odor that result from geosmin and MIB are an aesthetic quality; it is not a health concern. Union County Public Works monitors for more than 180 contaminants and performs more than 320 water quality tests per month on average to ensure the water meets all state and Safe Drinking Water Act (SWDA) standards.

Why do some customers notice a difference in taste or smell and others don’t?

Generally, the concentration of geosmin and MIB is low, but occasionally the levels may spike to several hundred parts per trillion. To put this in context, the general threshold for human detection is about 15 parts per trillion; however, people with sensitive pallets can detect geosmin or MIB in drinking water at concentrations as low as 5 parts per trillion. This is why some customers notice the taste and odor while others do not.

What can I do to improve the taste or odor at home?

There are ways to help reduce the smell and taste at home. Consider chilling water and/or adding lemon. In addition, some people use carbon filters – the type used in water pitchers or attached to faucets.

How can MIB and geosmin be treated through the water treatment process?

When higher-than-normal levels of MIB and geosmin are detected, water treatment plants utilize several strategies to mitigate the taste and smell. Activated carbon is implemented to reduce algae levels. The treatment plant can also draw water from lower depths in the water reservoir to minimize the algae intake.