High MIB Levels in Drinking Water - Update

Information Release for Cobb County-Marietta Water Authority's Customers Regarding High MIB Levels in Drinking Water

December 4, 2025

The Cobb County-Marietta Water Authority (CCMWA) continues to experience high levels of MIB (2-Methylisoborneol) at the Quarles Drinking Water Treatment Plant.  Its source water, the Chattahoochee River, reached a record high concentration of 137 parts per trillion (ppt) of MIB in November and has remained high.  For comparison, the highest level recorded in 2024 was 19 ppt.  All drinking water utilities in the region that withdraw water from Lake Lanier or the Chattahoochee River are facing similar challenges.

MIB is produced by algae and can give drinking water an earthy or musky taste and odor.  To reduce the impact of MIB to customers, CCMWA continues to shift water production to the Wyckoff Drinking Water Treatment Plant and thus limit the number of customers served by the Quarles Plant.  In addition, the Quarles Plant is applying powdered activated carbon (PAC) at its maximum design capacity to mitigate taste and odor issues.  While PAC provides significant improvement, its ability to remove MIB is limited, and MIB levels in the finished water will remain noticeable to sensitive customers.

CCMWA has allocated funding and staffing resources to begin evaluating advanced water treatment processes in 2026 to improve future taste and odor control.  In the meantime, CCMWA continues to monitor MIB levels daily and make operational adjustments as needed.

There is no health concern associated with MIB at these levels.  Your drinking water remains safe.

Customers can take actions to reduce the unpleasant taste and smell of water.  An activated carbon filter (such as Brita or Pur) can improve the water's taste.  Getting water from the refrigerator's water dispenser, chilling the water in the refrigerator or adding lemon juice before consumption can also help.

If you have any questions or concerns, please do not hesitate to contact us at (770) 514-5300 or your water service provider.