Georgia Wildlife Federation

Did you know that the average person in the United States uses around fifty gallons of water each day just while at home? About thirty-seven gallons (75%) is used in the bathroom: bathing, showering, brushing teeth, and flushing the toilet. Another seven gallons (14%) is used doing laundry, and the remaining six gallons (11%) is used in the kitchen for cooking, drinking, and washing dishes.* This water comes safe and clean into homes all across American everyday. So where does it come from? And how is this vast amount of water made safe and clean for millions of Americans everyday?

Generally speaking, the water that comes into your home is either from surface water (rivers, lakes, reservoirs, etc.) or groundwater (underground water accessed by a well). The majority of Americans, sixty percent, get their drinking water from surface supplies.** But what happens to this water between the source and the kitchen faucet? In order to illustrate this process, we toured Cornish Creek Water Treatment Facility here in Covington, Georgia. This facility draws water from Lake Varner, an 820-acre reservoir, and supplies seventy percent of the drinking water for Newton County and forty percent for neighboring Walton County. At full capacity, the facility produces seven and a half million gallons of drinking water each day and is making improvements to double that capacity to fifteen million gallons.

The treatment process begins as water is pulled in from the reservoir and treated with potassium permanganate. Potassium permanganate oxidizes any soluble iron and manganese that may be in the water, changing it to an insoluble state and making it easier to remove. Iron can cause water to taste bad and can stain laundry and plumbing fixtures red. Manganese can stain these things black and can react with chlorine to turn water brown – not too appetizing! As the water enters the treatment plant, aluminum sulfate is added. This chemical causes dirt, bacteria, and other particles to clump together, forming "floc", so that they can be removed easily. Lime and sodium bicarbonate are added to aid in this process. Chlorine is added to kill germs and powdered activated carbon is added to absorb taste, odor and organic compounds. All these chemicals are mixed into the water in a large chamber called the rapid mix.

Treated water from the rapid mix is then sent to the clarifiers. Different treatment plants use different types of clarifiers; Cornish Creek Water Treatment Facility uses up-flow clarification units. The water, which at this point contains flocked particles, enters the bottom of the clarifier and is forced up through the chamber in pulses. These pulses are created by a pulsation chamber which the water passes through before entering the clarifier. Floc forms in a blanket in the middle of the clarifier and stays in suspension as the water flows up through it. As the blanket grows in thickness, it rises to a point where it rolls into a sludge concentrator. Every thirty minutes, the floc in the sludge concentrator is "blown down" into side chambers and then sent to the sludge pond where it settles out and dries. The "floc-free" water is then pulled off the top of the clarifiers and sent to the pre-filter mix.

In the prefilter mix, the water from the clarifiers is equally divided up and sent to the filters to remove any remaining particles. Each filter is over four feet thick: eighteen inches of anthracite coal, twelve inches of sand, three inches of garnet, and eighteen inches of different-sized gravel. These filters are kept clean and functioning by "backwashing" them whenever they get dirty and allow water to pass at too low a rate. Backwashing can occur at any time but is generally conducted every ninety hours. It is done by forcing water and air up through the filter opposite of the normal direction of flow. This removes any trapped particles which are then sent to the sludge pond with floc from the clarifiers.

After filtering, the water is sent to the postmix where it receives final preparation before distribution to the community. Fluoride is added to strengthen consumer’s teeth and chlorine is added for disinfection, killing bacteria, viruses, and some protozoa. The water is also treated to keep the pipes within the city system and private homes free from corrosion, protecting water quality and lengthening the life of everyone’s plumbing. Phosphate is added to control corrosion and prevent lead and copper from leaching into the water. Soda ash is used to adjust the pH of the finished water to 7.2 also to help prevent corrosion. After treatment in the postmix, water is stored in the clearwell before being distributed to the city and county water systems.

So how can we be certain that the water coming out of the clearwell is cleaner and safer than the water coming in from the reservoir? The treatment plant constantly tests the water at every step of the process to ensure that the water coming into homes and businesses is clean and safe. At two points, the plant conducts computerized particle counts: at the clarifiers and after the filters. These counters track the number of particles in the water that are between three and fifteen microns in size, which would include the harmful protozoa Giardia and Cryptosporidium. A spike in the number of these particles would alert plant operators that something is wrong and quick action could be taken. Plant operators also regularly test for other chemical parameters in the raw and finished water and at three points during treatment. These tests measure pH, turbidity, temperature, aluminum, chlorine, phosphate, iron, manganese, alkalinity, and hardness. In addition, the Georgia Environmental Protection Division of the Department of Natural Resources annually tests the water for 167 different parameters. Finally, to ensure that water is as clean and safe entering the home as it is leaving the plant, the water is tested at dozens of locations throughout Newton County.

*Symons, Dr. James M., Plain Talk About Drinking Water, American Water Works Association, Denver, 1997, p 97. ** Ibid., p 129.