Granular Activated Carbon (GAC) is one step in the GCWW water treatment process. It is considered the best way to remove organic materials from water. 

After settling and filtration, water at the Miller Plant is filtered through beds of GAC. Millions of pores in GAC capture (or "adsorb") the organic substances removing them from the water. Most spills in the Ohio River are organics.

• One cup of GAC has the surface area of about 25 football fields (1,300,000 square feet).

• Water treated by GAC needs about 2/3 less chlorine than without GAC.

• GCWW "reactivates" carbon (burns off contaminants) in two giant 1,500°F furnaces.