Built in 1888, Sweetwater Dam is 127 feet high and allows the reservoir to hold up to nine billion gallons of water. The reservoir is protected by a diversion system which traps polluted and low-quality local runoff.
Chlorine dioxide is added to untreated water to kill bacteria and viruses in the water.
Ferric chloride and cationic polymer are quickly added and mixed into the water to begin the process of removing dirt and particles.
During the flocculation process, polymers and ferric gently mix, causing the dirt particles to stick together to form clumps. The iron in the ferric causes the floc clumps to turn an orange, rusty color.
Dissolved Air Flotation (DAF) System
The DAF basins provide a reaction zone where tiny bubbles are added into the water. The air bubbles catch onto the coagulated particles causing them to rise and float; this forms a sludge blanket on top of the water. The sludge blanket hydraulically floats to a desludging basin, where it is removed. Meanwhile, the clarified water travels below the sludge blanket to the sediment basins.
The sedimentation basin is where most of the remaining particles sink to the bottom. By the end of this stage, 85 to 90% of the particulate matter will have been removed.
The sedimentation water travels to gravity filters where it flows downward through a layer of anthracite coal and sand (to remove fine particles). The filters are periodically cleaned by a backwash procedure.
The clear well stores ten million gallons of clear, clean drinking water until it enters the distribution system which delivers it to our homes, schools, and businesses. The Clear Well and other enclosed "reservoirs" in the system help assure that Sweetwater Authority can meet customers' demands even during peak use times which exceed the Perdue Plant's 30 million gallons a day capacity.