Cobb-Marietta Water Authority plans to improve water taste

Jun. 24—Does your tap water taste or smell funky? If so, the Cobb-Marietta Water Authority is trying to fix that.

Although the water pumped out of the Chattahoochee River that eventually ends up in Cobb County homes has been treated for safe drinking, poor taste and odor can result from organic compounds in the water, said Rita Neely, the authority's engineer overseeing a project to improve the water's taste and smell.

Those issues are the result of naturally occurring compounds such as geosmin and methyl-isoborneol (MIB), which cause a musty, earthy taste and odor in the water.

"They don't actually pose a health risk, especially at the very, very low concentrations that we see them at," Neely said. "It's more of just an aesthetic issue with the water. But as we all know, anytime you're dealing with public confidence, even aesthetic issues can be concerning."

A webpage explaining the two compounds on the water authority's website advises customers to add lemon juice or chill their water in a refrigerator to improve taste, but Neely and her colleagues are also working on more proactive solutions.

Enter powder activated carbon treatment, which filters and improves the taste and scent of water. The authority plans to build a tower that will act as a PAC silo at its intake facility on Johnson Ferry Road, on the shores of the Chattahoochee.

The tower itself will be 47 feet tall and 13 feet in diameter. The authority has budgeted $5 million for the PAC treatment equipment, though a bid has not yet been sent out, and Neely said the cost could end up being closer to $4 million. If construction on the tower and associated equipment begins later this year, as is hoped, the project could be completed by the end of 2022, she said.

For now, the water authority is finishing up the design phase. At a meeting of the authority's board Monday, board members weighed different options for the tower's appearance — it may be painted grey, blue or green. Board members agreed grey blended with the background area better but also liked blue. The authority discussed having writing on the tower. If traveling north into Cobb motorists would see "Welcome to Cobb County" on the tower, if traveling south they would see the authority's logo.

"By virtue of having the Cobb County Commission chair on our board, I think we might be well served to put this decision off for a month, and have Ms. (Lisa) Cupid's input into it," said the board chair, James Scott Jr. The board concurred and delayed a decision on the paint color as Cupid was not at the meeting.

PAC treatment is similar to granular activated carbon treatment, often used to filter water in refrigerators and in the filtered water jugs made by companies such as Brita.

With GAC, "you're just running the water through that, and it has an opportunity to have small things kind of be absorbed by the carbon," Neely said.

The authority's Hugh A. Wycoff treatment plant, which pulls water from Lake Allatoona, has GAC equipment that can filter the water after it's been treated and made safe — the authority does so especially when levels of musty-tasting compounds are higher. But much of the water Cobb Countians drink comes from the James E. Quarles treatment center, which pulls water from the river, and does not yet have GAC or PAC treatment.

On any given day, depending on the needs of the system, water can be pumped to your home from either facility, no matter where in Cobb you are. Hence the desire to bring the Quarles center up to par with Wycoff.

The PAC treatment system, unlike the GAC treatment, will add smaller, finer particles of carbon to the water as its drawn from the river. As the water travels via pipelines to the Quarles facility, the carbon mixes with the MIB and geosmin. At the facility, the water will then sit in a reservoir, allowing the heavy carbon particles to float to the bottom before it is treated to make safe.