The treatment process
consists of a series of steps. First, raw water is drawn from the Cape
Fear River and sent to a 60 million gallon reservoir, which allows some
of the sediment to settle out prior to treatment.
Also, the reservoir provides a ten day supply of raw water in the case that a emergency situation arises and we are unable to pump raw water from the Cape Fear River.
After settling in the reservoir, the water then goes to a mixing tank where aluminum sulfate, sulfuric acid, and a cationic polymer are added. The addition of these substances cause small particles to adhere to one another (called "floc") making them heavy enough to settle into a basin from which sediment is removed.
Chlorine is then added for disinfection and sodium hydroxide is added for pH adjustment.
At this point, the water is filtered through layers of fine coal and silicate sand. As smaller, suspended particles are removed, turbidity disappears and clear water emerges.
Chlorine is added again as a precaution against any bacteria that may still be present. (We carefully monitor the amount of chlorine, adding the lowest quantity necessary to protect the safety of your water without compromising taste.)
Finally, sodium hydroxide (used to adjust the final pH and alkalinity), fluoride (used to prevent tooth decay) and a corrosion inhibitor (used to protect distribution system pipes) are added before the water is pumped to elevated water tanks, your home, or business through disinfected water lines.