The Sanford Water Filtration Facility is a state-of-the art water purification plant located about 1.5 miles from the Cape Fear River. 

The facility is currently certified to produce 12 million gallons per day of top quality drinking water. However, an extensive upgrade and expansion project is underway to more than double that output capacity. When the project is complete, the facility will be able to produce 30 million gallons per day.

Construction has already begun on the $400 million expansion project. It's expected to be completed in 2028.

The Water Process

1 - Collection

A raw water pump station is located on the Cape Fear River at NC-42.

The pump station has three 250 horsepower pumps that grab water as it flows downstream and sends it 1.5 miles to the Sanford Water Filtration Facility.

2 - Reservoir Storage

The raw water is pumped into a 60 million gallon raw water reservoir located at the highest elevation on the Sanford Water Filtration Facility grounds. 

This reservoir is the beginning of the water filtration process. It allows for presettling, in which some sediment and other heavy particulates separate and fall to the bottom of the reservoir. Presettling results in higher water quality and helps reduce the amount of chemicals and energy needed to create pristine drinking water. 

Water typically sits and settles in the reservoir for a few days (up to 10 days). A controlled release then sends it downhill into the basement of the filtration facility. 

3 - Coagulation & Flocculation

As the water flows through a 36-inch pipe into the facility, two chemicals are added: Aluminum sulfate and sodium hydroxide. Aluminum sulfate is a coagulating agent, which promotes clumping of particles in water and thus makes it easier to separate those particles from the water. Sodium hydroxide is a strong base used to reduce the acidity of the raw water, raising the pH level to optimal ranges.

With those chemicals properly mixed into the water, it's time for more mixing. This time the mixing takes place in flocculators. 

Sanford Water Filtration Facility has a series of flocculators designed to mix the water at different rates. The first flocculators spin at the highest rate of speed. The mixing speed slows down in each subsequent flocculator basin. This controlled mixing combined with the aluminum sulfate causes particles in the raw water to clump into larger groups called "floc."

4 - Sedimentation

At the end of the flocculators, the water flows into a large trough at the entrance of the sedimentation basins. The water can then be released into the sedimentation basins as needed.

Once in the sedimentation basins, time and gravity take over. The floc that formed from the previous process settles out to the bottom of the basin forming sludge. The sludge is regularly pumped out to a gravity thickener and put through a belt press to remove water so the sludge can be shipped off and reused by other industries.

When the settled water at the top of the sedimentation basin reaches the end of the basin it flows over a weir wall and into another tough. 

In this trough, small amounts of sodium hydroxide and sodium hypochlorite are added as needed. The sodium hydroxide (again) raises the water's pH level. The sodium hypochlorite is a disinfectant that eliminates harmful microorganisms.

At this point, most contaminants in the water have been removed.

5 - Filtration

To finalize the purification process, the water is now pushed through heavy duty multimedia filters.

The filters use layers of gravel, anthracite coal and silicate sand to remove any remaining impurities.

6 - Disinfection

The filtered water then has four more chemicals added to it: sodium hydroxide (pH level), sodium hypochlorite (disinfectant), phosphate (corrosion inhibitor), and hydrofluorosilicic acid (public health).

Plant operators monitor and adjust sodium hydroxide and sodium hypochlorite levels as needed to control the water's pH level and eliminate any harmful microorganisms. Phosephate is a corrosion inhibitor that helps form and maintain a protective barrier on the inside of pipes; this helps prevent the release of lead and copper that may be locked in old pipes or fittings along the water distribution system. Hydrofluorosilicic acid is maintained at recommended levels as has been advised by U.S. health officials since the 1940s. Those guidelines have proven wildly successful across the country--even leading to fluoridation of drinking water being named a top 10 public health achievement in the 20th century.

7 - Storage

The water then arrives in a clearwell capable of holding up to 1.8 million gallons of finished water. 

The clearwell is the final stage of the water purification process. It stores the finished water and allows disinfectants to fully activate.

8 - Distribution

Water from the clearwell is pumped into the distribution system as needed to serve TriRiver Water customers.

Testing Process

Water quality is tested at every stage of the treatment process. 

A state-certified laboratory is located on site at the Sanford Water Filtration Facility. Certified technicians work around the clock -- performing hundreds of tests every single day -- to make sure each step of the process is working optimally and every drop of finished water that leaves the facility meets the highest regulatory standards.

In addition, laboratory staff test tap water at 50 different sites across the distribution system every month. These tests help our experts monitor water quality at your tap, not just inside the filtration facility, ensuring that the water is flowing through the distribution system as expected.

If you notice any changes to your water or have any concerns about your water quality, you can call the filtration facility at (919) 777-1803.