Water Treatment Process

Before arriving at your tap, water is treated at the Hanahan Water Treatment Plant to remove sediment, bacteria, and other impurities.

The plant is a member of the Partnership for Safe Water and meets or exceeds all water quality standards.

Water Sources

Water from the Bushy Park Reservoir and the Edisto River flows through deep tunnels to our Hanahan Water Treatment Plant. Read more about our source water here.

Rapid Mixing

Once it arrives at the plant, the pH is adjusted and water is rapidly mixed with aluminum sulfate (alum), a coagulant that helps the impurities stick together to form bigger particles called floc.


After rapid mixing, the water flows into flocculation basins, where the flow of water is slowed and the floc has time to grow bigger.


Next, the water flows into sedimentation basins, where the heavy floc particles sink to the bottom and are removed.


Now the water travels through large filters made of sand, gravel, and anthracite. Filtration removes any remaining microscopic particles and microorganisms.


Finally, the water is disinfected to protect it against bacteria. Charleston Water System uses chlorine dioxide and a combination of chlorine and ammonia called chloramines to disinfect the water. Fluoride is also added support good dental health.


The clean water is then pumped into pipes that deliver it to more than 110,000 homes and businesses in the Greater Charleston area.

Video tour of the treatment process

Hanahan Water Treatment Plant

Hanahan Water Treatment Plant

Piping below the filters, Hanahan Plant

Piping under the filters, Hanahan Water Treatment Plant