Water Quality & GAC
At the Town of Pittsboro, we prioritize the health and well-being of our residents. One of our central commitments towards this goal is ensuring our community has access to the highest quality drinking water we can provide. This page is designed to give information about our water treatment process, the Town’s Granular Activated Carbon (GAC) filtration system, and test results showing the outcome of our efforts to provide the best drinking water.
About the Town’s Water Treatment and Distribution System
- Our Water Treatment Plant is located at 3746 Hwy 15-501 N, Pittsboro, NC 27312.
- Between our storage tanks, clear well, and the storage capacity of our lines, the Town has nearly 3 million gallons of clean water storage capacity.
- Our Water Treatment Plant staff have been awarded the Area Wide Optimization (AWOP) Award numerous times over the past decade. The AWOP Awards are given annually to water systems demonstrating outstanding turbidity removal, a key drinking water quality test.
- While all drinking water systems must meet strict state and federal drinking water standards, Pittsboro’s system has met high-performance goals far exceeding state and federal standards.
- Our Water Treatment Plant can produce 2 million gallons of drinking water daily, nearly double our average daily water use.
How Does the Town Process and Treat Drinking Water
Municipal drinking water systems are a combination of professional, knowledgeable staff, expansive infrastructure, and complex chemistry. Each element comes together to collect, treat, purify, and distribute drinking water, making it safe for consumption. This complex process ensures that every drop of water reaching our taps is as free from contaminants and pathogens as possible.
- Collection: Raw water is drawn from the Haw River near the Bynum Bridge and pumped to the Water Treatment Plant via large underground pipes. The raw water is pumped into a large storage area where the coagulation and flocculation processes begin.
- Coagulation and Flocculation: We use coagulation and flocculation processes to begin our water treatment. Special chemicals, known as coagulants, are introduced to the water. Through a system of multiple agitators spinning at different speeds, the coagulants bind with dirt, debris, and other dissolved particles, creating larger, cohesive particles called “floc”. The water in the tank is then settled.
- Sedimentation: Following coagulation, the water is allowed to settle. The heavier floc particles, laden with organic solids and contaminants, sink to the bottom of the tank due to gravity. This sedimentation process ensures that most of the contaminant particles are separated, leaving clearer water on top.
- Filtration: The clearest water from the top of the sedimentation tank is then directed through a series of filters. These filters, made of sand, gravel, and charcoal, act as sieves, trapping even microscopic contaminants. This stage is crucial as it removes remaining particulate matter, bacteria, and certain pathogens.
- Disinfection: Once the water has been filtered, it's essential to ensure it's free from harmful microorganisms. Disinfectants, or chemical agents that neutralize bacteria, viruses, and other pathogens, are added to ensure that the water is safe for consumption. Once the disinfection process is complete, substances used to protect the inside of our distribution system are added, and the disinfected water is pumped to a “clear well”, which is a clean water storage tank, before being pumped to the Granular Activated Carbon (GAC) system.
- Granular Activated Carbon (GAC) Filtration: The water is pumped from the clear well to the GAC filter, where the advanced filtration process begins. The water is pumped into the top of the GAC filter, which consists of activated carbon in small pellets arranged in a 28’ tall cylinder. As the water flows through the GAC filter, the pellets adsorb per- and polyfluoroalkyl substances, or PFAS. The Town is currently experiencing between 93% and 99.9% removal of these various emerging contaminants.
- Storage and Distribution: Post-GAC treatment, the water is returned to clean wells. This storage supplies the distribution network and provides a buffer against increased demand or reduced supply. From these storage facilities, water is pumped into the distribution system, a network of pipes that delivers water to homes, businesses, and other establishments in Pittsboro.
About the Granular Activated Carbon (GAC) Advanced Filtration System
As we learn more about emerging contaminants and ways to protect against them, the Town implemented a Granular Activated Carbon (GAC) filtration system. This section provides an in-depth understanding of GAC and its pivotal role in water purification.
- Understanding GAC: GAC is derived from organic materials like coconut shells or coal. These materials undergo a carbonization process, followed by activation using super-heated steam. The result is a highly porous material with a large surface area, ideal for adsorbing various contaminants.
- Why GAC?: Traditional water treatment processes, while effective at removing traditional contaminants, may not remove certain organic compounds, chemicals (such as PFAS), or micro-pollutants. GAC's unique adsorptive properties make it very efficient at capturing these contaminants. Moreover, GAC effectively removes unpleasant tastes and odors, ensuring water is safe and has a pleasant taste and smell.
- The GAC Process: Water is passed through granular activated carbon beds. As water flows through, contaminants are adsorbed onto the carbon particles. Adsorption means that the contaminants stick to the outside of the filtration media. Over time, as the outside of the carbon pellets become saturated with contaminants, they are removed and then regenerated off-site. This recharge is done in an environmentally sustainable way, with the process not releasing any of the collected PFAS into the environment. The Town maintains two separate GAC filters at our water plant but only uses one at a time. This means that as soon as our water treatment plant staff find evidence that the GAC is starting to experience a “breakthrough,” or the presence of PFAS in the lower level of the filter, we can switch to the other filter and continue to have 100% GAC treatment while the media in the used tank is replaced and regenerated.
- Benefits of GAC: Beyond its superior contaminant removal capabilities, GAC offers multiple benefits. It acts as an added layer of purification, ensuring water quality consistency. GAC systems are also sustainable, with a lower environmental footprint than other advanced treatment methods. Furthermore, GAC-treated water often has a fresher taste, enhancing the drinking experience.
- GAC in Pittsboro: To provide the highest quality drinking water for our customers and residents, the Town of Pittsboro has dedicated significant time and money to implementing a GAC filtration system. The Town conducted numerous engineering and operational studies and ensured staff received training to integrate GAC into our water treatment process seamlessly. Our GAC facility operates round the clock, treating every drop of water the Town produces daily. The result is a significant enhancement in water quality, setting new standards in municipal water treatment.
- How Much Did the GAC Cost: At nearly $3.5 million, this significant investment is one of the largest single infrastructure projects undertaken within our utility program, with funding coming from the town’s revenue and grant funding. Grant funding included
Water Quality Test Results
To underscore our commitment to transparency, please see below for a sample of test results from before and after GAC implementation and a list of all our testing results since we implanted the GAC.
Comparison of Raw vs. Finished Water w/ GAC
No Samples Taken Due to Ammonia Burnout (process to remove access ammonia from the water system - done yearly as a legal requirement).
No Sample Due To Changing Testing Providers
|Early August, 2023|
|Late August, 2023|
Pittsboro's dedication to water quality remains unwavering. With our advanced treatment processes and the integration of the GAC system, we are at the forefront of ensuring the best quality water for our customers and consumers. We invite our community to stay informed and take pride in the high-quality water they consume daily.
To sign up for Water Alerts, visit www.pittsboronc.gov/news and choose “NOTIFY ME”
For further inquiries or feedback, please email Colby Sawyer, our Public Information Officer, at firstname.lastname@example.org.
This page will be updated as additional information is obtained or frequently asked questions are answered, so check back regularly.
Last updated: 11 September 2023