Guest blog by Brian Smart and Katharine Callaway
The 330,000 plus residents of Charleston County use approximately 114 million gallons of water per day (Mgal/d) only about 12 percent of which is from ground water sources. The other 101 million gallons come from surface water sources, mainly the Edisto River and Bushy Park Reservoir. This raw water is subject to runoff from rainwater, agriculture, industry and air pollution, which deposit chemicals, bacteria and organic contaminants in the streams and rivers feeding the lakes and reservoirs. Intensive treatment is necessary before the surface water is suitable for human consumption. 
The water treatment plant in Hanahan has the responsibility of making our water safe to use. After being screened to remove large objects such as tree branches, dead animals and garbage, a combination of chlorine and ammonia is added to the water to kill bacteria and viruses, and lime is added to adjust the pH levels. Next, aluminum sulfate is mixed into the water, acting as a coagulating element to bond with the previously added chemicals, now dead bacteria, viruses and other microscopic material and cause them to drop out of the water stream as sediments. These sediments are disposed of by spraying them on a forested area near the water treatment facility. Finally, the water is passed though a series of fine mineral filters and then treated with more chlorine, ammonia and lime, as well as fluoride to keep your teeth healthy and orthophosphate to prevent heavy metals from leaching out of your plumbing. If anything can live through this process, it must be a very tough organism indeed.