Why Does Atlanta Tap Water Smell Like Earth?
Residents across metro Atlanta are reporting that Atlanta tap water has taken on an unusual earthy or musty odor and taste as the fall season approaches. Water authorities have reassured the public that while the odor can be unpleasant, the water quality meets safety standards and is completely safe to drink.
This seasonal issue is directly related to algae activity in Lake Lanier, a primary water source for metro Atlanta. As algae increases in the late summer and early autumn, it releases two natural compounds known as 2-methylisoborneol (MIB) and geosmin. While these compounds are not harmful to human health, they can cause a distinct earthy or moldy taste and odor even at extremely low concentrations.
Understanding MIB Levels and Water Treatment
According to a recent notice sent to residents by the Forsyth County Water Department, raw water measured an MIB concentration of 213 ppt (parts per trillion) during testing on the 1st of the month. After undergoing rigorous treatment processes, the level dropped to 22.3 ppt in the water supplied to local households. Because humans can detect MIB at concentrations as low as 10 ppt, some residents may notice a change in taste and smell even though the water is fully treated.
This recurring issue is not new to the region. Last November, the Cobb County-Marietta Water Authority recorded an MIB concentration of 137 ppt in the Chattahoochee River, marking a record high that significantly exceeded the 19 ppt peak measured in 2024. To combat these seasonal taste and odor problems, local water departments are continuously upgrading their treatment facilities. Forsyth County currently utilizes an advanced ozone treatment process, which may occasionally impart a chlorine-like taste that officials confirm remains entirely safe for consumption.
