Millions of metro Atlanta residents may notice their tap water smells or tastes earthy or musty this fall. Water officials say the water is safe to drink.
What’s happening: Every fall, Lake Lanier, the main drinking water source for the Atlanta region, goes through a natural process called lake turnover. During summer, the lake separates into layers: warm water on top, cold water on the bottom. As the air cools in autumn, the surface water gets colder and heavier and sinks, mixing with the bottom layers. That mixing stirs up two naturally occurring compounds, geosmin and 2-methylisoborneol, that algae and bacteria produce in the lake sediment. Those compounds are what give the water its earthy or musty smell and taste.
What’s new: Concentrations of both compounds are running higher than usual this season. Water treatment plants are built to handle low levels of these compounds, but the current levels are high enough that some taste and odor is getting through even after treatment.
“Our processes typically treat the taste and odor issues related to these compounds when they are present at low levels,” Gwinnett County officials said. “However, during certain periods of the year when the levels of these compounds are at their highest, some taste or odor issues may remain.”
What’s confirmed: The compounds are not harmful. Gwinnett County officials said the water “continues to meet all state and federal drinking water standards and is safe to drink.” The same conditions affect water systems across the metro Atlanta area that draw from Lake Lanier.
What utilities are doing: Water utilities are increasing monitoring of both the lake and finished tap water and adjusting their treatment processes as conditions change.
What to know: This is a recurring seasonal issue for water systems that rely on Lake Lanier. It typically also occurs in spring.