August 2025 What's on Tap Employee Newsletter

Waste Not, Want Not

Recycling Wastewater for Potable Use By: Lily Soetebier , Coastwatch

The earliest evidence of wastewater reuse dates back 5,000 years to the Minoans, an ancient civilization that occupied modern - day Crete. Their sewage and stormwater systems fed water to their farmlands, keeping crops watered and fertilized during dry spells. While technology and sanitation have drastically changed over the course of the past 50 centuries, water reuse and recycling remain important issues today. Last spring, Whit Wheeler, the director of Raleigh Water, approached Emily Berglund and Tarek Aziz, professors of civil and environmental engineering at NC State University, to explore potential approaches that would make Raleigh Water more resilient to drought. Now, they have partnered to identify possible solutions for the city.

Defense Against Exceptional Drought Past threats to water resources sparked this collaboration, according to Berglund. “ From 2006 to 2008, the southeast ern region of the United States faced intense droughts, ” she says. For North Carolinians, the drought reached its most extreme in the fall of 2007. August of that year was the second warmest and driest the state had ever seen, which led to more than 60% of the state receiving an “ Extreme Drought ” classification by the start of September. That October, nearly 40% of the state experienced extreme water shortages, widespread loss of crops and pastures, and a high risk of wildfires. The U.S. Drought Monitor placed these areas under the most severe “ Exceptional Drought ” classification. By December 2007, 14 water systems had less than a 100 - day supply of water in their reservoirs. The City of Raleigh ’ s solution, according to Berglund, was to increase the allocation from Falls Lake for its drinking water supply. “ It was a good solution, ” says Berglund, “ but it ’ s a Band - Aid. It has a limit. ” Current models predict a new water supply will be necessary between 2045 and 2067 — which is why Raleigh Water is already studying alternatives that include a new reservoir on the Little River in eastern Wake County and a withdrawal from the Neuse River. In addition, the research team is working with Raleigh Water on a new Community Collabora tive Research Grant project specifically to identify secondary water sources. “ If one source fails, or there ’ s a shortage, then we can rely more heavily on the other one, ” Berglund says. Reuse in Raleigh Water reuse is not new to North Carolina. The Neuse River Resource Recovery Facility (NRRRF) treats an average of 50 million gallons of wastewater per day — the equivalent of about 100 Olympic - sized swimming pools. The facility takes in wastewater from municipal sources — households, businesses, and other community establishments — and conducts “ advanced wastewater treatment. ” The primary stage of treatment filters out physical contaminants like debris, grease, and oils. Following this primary treatment the water passes through more advanced processes, during which it cycles between zones with and with out aeration, creating the right conditions for microorganisms to clean the water. These microorganisms consume organic matter and convert harmful ammonia - nitrogen to nitrogen gas, which dissipates freely from the water. After the nitrogen dissipates, the microorganisms are settled to the bottom of a tank, removing them from the treated water. Finally, in the “ tertiary ” stage, water passes through fine sand filters to further clarify it and then under ultraviolet lights for disinfection. (Cont ’ d)