Purple Pipes Provide a Green Solution

Sustainable Raleigh Spotlight Feature

News posted Sep. 22, 2016 - 6:00 am
Purple Pipes

The average City of Raleigh customer uses 80 to 100 gallons of water every day. Many of our daily habits involve water. When Raleigh residents wash their hands, flush the toilet or do their laundry, the water drains to one of the City’s wastewater treatment sites. Thousands of miles of pipe crisscross through Raleigh and surrounding areas, carrying an average of 49 million gallons of water a day to treatment plants.

But what if that same water was sent back to customers for special uses after treatment?

Most of the City’s treated wastewater flows into the Neuse River. However, some of it is diverted, given additional disinfection, and sent through a network of purple pipes.

The purple pipe indicates reclaimed water. “Irvine Ranch, CA was the first to use a reclaimed water system,” said Marla Dalton, the City’s reuse water coordinator. “They chose the purple because it distinguished them from sewer pipes (green) and potable water pipes (blue) and because the color had no current designation.”

The bright purple pipes stand out, not just for their color, but for the unique purpose they serve. The small network of pipes brings reclaimed water to commercial Raleigh customers. The reclaimed water is non-potable, meaning that it’s not used for drinking.

The biggest uses for the reclaimed water so far include landscaping, golf courses, toilet flushing and water for cooling towers in industrial settings.

“The reality is that one day, we could experience a water shortage,” said Dalton. “It just makes sense to have another water utility.” Dalton said that if a serious drought happened, the City could rely on the reclaimed water infrastructure for non-potable uses.

Recycling water also diverts nitrogen, which causes water quality problems, from being discharged into the Neuse River. “The more we recycle water, the less nitrogen we put into the river,” said Dalton.

The reuse water network covers a small part of southeast Raleigh and Zebulon. The program’s biggest customers are GlaxoSmithKline and the Carolina Mudcats Stadium in Zebulon, and NC State’s Centennial Campus in Raleigh. They all use reclaimed water for flushing toilets, cooling towers and landscaping.

Dalton said it’s relatively easy to install reclaimed water plumbing in new building construction. Changing the public’s perception of reclaimed water, however, is not always easy.

“We have a strong education program to help the public overcome negative perceptions,” said Dalton. “And it helps that we’re providing non-potable water at a reduced rate compared to potable water.”

Anyone outside the purple pipe district can pick up free reclaimed water from one of the City’s four storage areas, provided they have a container and a vehicle to haul it away. “We’ve seen people come in with anywhere from 200 to 2,000 gallon size tanks,” said Dalton. Most customers use the reclaimed water for landscaping, and a few use it for pressure washing.

The City is even growing crops with reclaimed water. The City’s farm, located at the Neuse River Resource Recovery Facility, has 350 acres of irrigated land, growing sunflowers for biofuel, corn, fescue, hay, soybeans and sorghum. Most of the crops are sold as animal feed at a discounted price.

“We’ve seen a definite benefit from the regular irrigation,” said Dalton, “Our yields are higher and our crops are more stable and soil nutrients such as nitrogen are better utilized.”

The City’s website has more details on the reuse water system and video called “Once is Not Enough” explaining the process of reclaiming water.

This Sustainable Raleigh Spotlight is one in a series of City of Raleigh sustainability stories.

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