Water is withdrawn from Lake Lanier through large intake pipes. The lake water is then stored in equalization basins or reservoirs at each facility to provide process flow rate stabilization. In other words, these lake water holding basins balance the rate of water production depending on the county’s current water supply needs.

The initial step in the water treatment process is ozonation. Ozone is created by combining pure gaseous oxygen and electricity through a series of complex operating systems. Its primary purpose is disinfection as well as oxidation of compounds to improve water clarity, smell, and taste.

In the next step of the treatment process, chemicals called coagulants are introduced and the water is rapidly mixed so as to form "sticky" receptors which cause small particles to clump together. “Rapid mix” is just as it sounds: rapidly mixing the water to blend the chemicals together quickly. Flocculation involves successively slower mixing to further develop the suspended particles or "floc" that is captured by filtration in the succeeding step.

Filtration is the most important and regulated step in the treatment process. Our unconventional filter plants use direct filtration, which means we omit a sedimentation phase seen in most water treatment plants. We are able to do this because of the exceptionally clean and unchanging source of water from Lake Lanier.

Our filters are comprised of large rectangular vessels filled with a dual media of anthracite carbon and sand.  The particles created in the previous treatment processes are physically captured or intercepted through adsorptive and absorptive forces within the filter media. There is also a biological component, where the “biomass”—a group of tiny organisms—consumes organic and inorganic compounds broken down by the ozonation process.

After filtration, the water receives a final treatment of beneficial or "finishing" chemicals including lime (pH control), fluoride (dental health), corrosion inhibitor (pipe protection), and chlorine (disinfection).

The last step in the process is finished water storage and pumping. Water is stored at each filter plant in large tanks called clearwells before being pumped into our huge network of pipelines and supplemental storage tanks located throughout the county. Each critical step in our treatment process guarantees safe, secure, and plentiful water at every tap!

Shoal Creek Filter Plant

• Georgia Association of Water Professionals, Plant of the Year Award
  • Award won in 2007, 2013, 2014, and 2017
  • Georgia Association of Water Professionals, Perfect Compliance Record
    • Gold Award (awarded once per year) received eight times
    • Platinum Award (awarded once every five years) received twice

Lanier Filter plant

• GA Association of Water Professional, Perfect Compliance Record
  • Gold Award (awarded once per year) received four times

Gwinnett County’s filter plants are two of only four facilities in Georgia that use ozone in their drinking water treatment process. Ozone is a powerful oxidant (chlorine and hydrogen peroxide are also oxidants) with a much higher oxidation potential than chlorine. This oxidizing power is what gives it its disinfecting power—the ability to kill viruses, microbials, and other pathogens. It improves the clarity of the water and removes algal toxins.

Ozone also removes dissolved organics like taste and odor compounds, residuals from pharmaceuticals, and more. It breaks down these organic compounds into smaller pieces that can be used as food by the biomass on the filters during the direct filtration stage of the process. Consider this example: if you wanted to eat a steak, you could eat a lot more of it—and much faster—with a knife and fork to break it up into bite-sized pieces rather than trying to eat it whole. The ozone acts as the knife and fork, breaking down longer chain organics into shorter ones that the biomass can then consume.