Metro Atlanta’s smelly drinking water means fall is in the air

Fall has arrived in Atlanta: The leaves are flecked with red and orange, the air is crisp, and the water smells awful.

No, it’s not just you. For much of metro Atlanta lately, drinking a glass of water has felt like sipping on a medley of dirt and mold, like none of your cups are getting cleaned quite well enough.

But the culprit is not mildew or bacteria, and water utilities and experts alike say the water is still safe to drink, even if the taste and odor are unpleasant. Instead, the problem is the byproduct of the slow autumn churning of Lake Lanier, the region’s most important source of water.

The musty funk is a rite of fall, caused by the lake’s cooling temperatures and sent coursing through millions of taps from Gainesville to Atlanta. But it has been particularly prevalent this year, turning up noses even as utilities try to counteract the taste with carbon filters and ozone gas.

“It has spiked and then spiked and then spiked again,” Fulton water quality manager Cynthia Dang said in a video posted to YouTube on Tuesday.

The culprits are compounds called 2-Methylisoborneol and geosmin, a molecule whose name is derived from the ancient Greek words for “earth” and “smell.” Georgia Tech professor Ameet Pinto, who studies microbes in drinking water, said humans are extraordinarily sensitive to the compounds, enough that they could smell a few drops spread through millions of gallons of water. But that doesn’t mean it’s unsafe to drink.

Pinto said the compounds usually come from algae growing near a lake’s surface or bacteria in the sediment deep below. For most of the year, they stay in their place: As the summer sun beats down on the lake, the warm surface water floats on top of the cold water below. Sediment stays on the bottom, algae on the top.

Then the summer heat breaks. The top layer of the lake begins to cool and sinks to the bottom, and the lake slowly churns, mixing the smelly byproducts from top to bottom.

About 70% of metro Atlanta’s residents get their drinking water from Lake Lanier. (File 2020)

About 70% of metro Atlanta’s residents get their drinking water from Lake Lanier one way or another. Some utilities, like Gainesville and Gwinnett County, pull straight from the lake. Others, like the city of Atlanta, draw water downstream on the Chattahoochee River.

And for some reason, more of them seem to be noticing the water’s mildewy smell this year.

Jessica Sterling, the technical programs director at Chattahoochee Riverkeeper, started hearing about it in the middle of September, when a coworker in Gainesville mentioned changes in their drinking water.

Then she noticed the funky water at home in Atlanta. Her neighbors started asking what was going on. People sent Riverkeeper staff messages wondering if something was wrong.

Something does seem different this year, Sterling said. The smell-producing compounds find their way into the water every fall, but they’re not always so pronounced. Often, she said, residents don’t notice them in downstream water systems like Atlanta’s.

But for some reason, the smell seems to be lingering longer than normal, even though the Riverkeeper’s tests of the lake didn’t detect unusually high algae levels this year.

The persistent odor has left water system officials scrambling to address complaints.

Gwinnett water resources director Rebecca Shelton said the county had managed to tamp down on complaints after pumping more ozone into the water, helping to break down the smell-producing compounds. A spokesperson for Atlanta’s watershed department said complaints are finally abating, but the department has activated carbon on standby.