Big Buffalo Water Reclamation Facility is a wastewater treatment plant located in Sanford. 

The facility utilizes the Biological Nutrient Removal (BNR) process to treat raw sewage and return that product back into the environment. It is permitted to discharge up to 12 million gallons of reclaimed water daily.

Homes and businesses in Sanford and Lee County that are connected to the sewer distribution system all send their waste to this facility. However, work is underway to connect Pittsboro to Big Buffalo as well. That connection is expected to be completed in late 2027.

While the water filtration process to create drinking water is a chemical process, the wastewater treatment process is a biological one. Wastewater plant operators utilize microscopic organisms -- bacteria, protozoa, and metazoa -- to break down and clean the wastewater. 

The Water Reclamation Process

1 - The Headworks

All sewage pipes throughout the city eventually flow back and dump into the headworks, a collection location that begins the water reclamation process at Big Buffalo. The sewage arrives and passes through bar racks and grit chambers. Bar racks are sturdy filters that catch and remove large debris like rags, toys, sticks and rocks. Grit chambers are settling tanks that allow heavier materials, like sand and gravel, to separate from the liquid sewage for removal. This debris and grit must be removed before the wastewater enters the facility's influent pumps, which send the remaining wastewater up to the BNR basins.

2 - BNR Basins

Big Buffalo has four Biological Nutrient Removal (BNR) basins. Each basin has five separate zones that use naturally occurring microorganisms and mechanically controlled air to remove elements like nitrogen, phosphorous and ammonia from wastewater. Those elements, if not properly controlled, could be harmful to the ecosystem when treated wastewater is discharged.

3 - Clarifiers

Partially treated wastewater from the BNR basins flow into the clarifiers. Big Buffalo has five separate clarifiers. Clarifiers separate sludge from the water by allowing the heavier sludge to fall to the bottom of the tank and the clear water to filter over weir walls into the next step in the process.

At this point the process breaks up into two different areas with the water continuing on in one direction and the sludge heading in another.

Water

A1 - Filter Facility

The clear water from the clarifiers flows into one of 14 tanks at the filter facility. Each tank has its own filter that works to remove fine particles remaining in the water. 

A2 - UV Facility

The cleaned, and now filtered, water flows through one of four channels filled with ultraviolet lamps. The lamps shine UV light throughout the water. The UV light is extremely effective at sterilizing any remaining bacteria, viruses and protozoa. Sterilization inactivates the microorganisms, thus rendering them harmless. Doing that is safer for the environment than using chemical disinfectants, which would then be in the water when it is discharged in the next step. 

A3 - Reuse or Discharge

Big Buffalo discharges its fully treated water into Big Buffalo Creek. The vast majority of the water treated at this facility is discharged back into the creek. However, some of the water is sent off to the Water Reuse Program. This program allows industries to tap in and use the water in specific ways. For example, Sanford Municipal Golf Course uses the water for irrigation. The Water Reuse Program curbs the area's overall water usage, frees up more discharge capacity for the facility, and extends the life of wastewater facilities.

Sludge

B1 - RAS/WAS Station

Sludge from the clarifiers arrive at this station and is evaluated. Plant operators look at the number and health of the microorganisms in the sludge. If the numbers suggest the sludge can be reutilized in the BNR process, it is labeled as Return Activated Sludge RAS) and sent back up the BNR basins. If the sludge cannot be utilized in the process again, it is labeled Waste Activated Sludge (WAS) and is sent on to the sludge storage tanks.

B2 - Sludge Tanks

Big Buffalo has four sludge storage tanks. They are used to hold sludge for further processing.

B3 - Gravity Belt Thickener

Sludge from the tanks will eventually be sent through the gravity belt thickener. This device pulls moisture out of the sludge. When the sludge is dehydrated to a specific consistency, it can head to the aerobic digesters.

B4 - Aerobic Digesters

Plant operators inject oxygen into the sludge and stir it up. This helps support the growth of microorganisms that help speed up the decomposition process. This process turns the sludge into biosolids, which can then be shipped to local farmers who participate in the land application program. As of 2023-2024, there were 43 fields in Sanford permitted for use of biosolids. During that year, 33 fields spread biosolids out across nearly 600 acres.