General Information

Ocracoke’s water plant: turning salt water to fresh

September 2015
By Anmargaret Warner

On Ocracoke, most homes have “city water,” but on an island 23 miles away from the mainland, what does that mean?

Most fresh water on Ocracoke comes the Ocracoke Sanitary District (OSD), also known as the water plant.

The plant began running in 1977 and was the first “reverse osmosis” plant in the state, said David Tolson, plant manager, who has worked there since 1978.

Before that, Ocracoke residents collected rainwater in cisterns or drew their own well water. The village water dripping from faucets originates from the bottom of a well, too.

Water plant manager Dave Tolson explains how the salty water is pushed through these membranes to filter the salt. Photo by C. Leinbach

Water plant manager Dave Tolson explains how the salty water is pushed through these membranes to filter the salt. Photo by C. Leinbach

Above the hum of the equipment inside the plant, Tolson explained reverse osmosis. “In Nature, osmosis is when salt water draws in fresh water,” he said.

“That’s why humans can’t drink salt water–because the salt water will draw in all of the fresh water and dehydrate you.”

At Ocracoke’s plant, the state-of-the-art, custom-designed equipment pushes the salt water through a membrane to take out the salt. “The fresh water goes out the other end and goes into storage tanks,” he said. The remaining salty water, called “concentrate,” is discharged into the Pamlico Sound.

“That water is actually less salty than the Sound water,” he said.  “So it doesn’t negatively affect wildlife in the area.” To get the raw water, three wells extract it from the Castle Hayne Aquifer more than 600 feet below ground. This water lens, stretching over 12,500 square miles in eastern North Carolina, is the most productive aquifer in the state. While its upper layers contain fresh water, its lower depths contains salt water from where the plant draws its water.

“The well water is still clean, but has salt and hydrogen sulfide in it, which gives off that rotten egg smell,” Tolson said.

Every water system is designed for the source of water you have to use because different membranes have to be used according to the saltiness of the water, he said. “Technology for reverse osmosis has gotten better over the years,” Tolson said.

The fresh water comes out the pipe labeled ‘permeate,’ and the reject water, labeled ‘concentrate,’ is discharged into the Pamlico Sound. Photo by C. Leinbach

The fresh water comes out the pipe labeled ‘permeate,’ and the reject water, labeled ‘concentrate,’ is discharged into the Pamlico Sound. Photo by C. Leinbach

The island’s population and development growth since the water plant’s beginning are intertwined: as island development progressed, so have the plant’s capabilities to keep up.

Yearly production at the plant climbed steadily through the early 80s and into the late 90s, before dropping off in the early 2000s.

Tolson suspects the decline in water usage began as customers upgraded their toilets and shower heads to use less water. “In the summer, the island uses about 300,000 gallons a day,” Tolson said.

That amount drops to 80,000 to 100,000 per day in the off season. Janie Garrish, secretary of the office, who has worked for the OSD for 34 years, thinks the aquifer and plant will be able to handle water needs on the island as they evolve.

“The quality of water hasn’t really changed in all of the years I’ve been here,” she noted. The OSD didn’t allow any new meters to be installed on the island before the latest update in 2010. “

The island grew faster than the water system was able to,” Garrish said. Since 2010, they’ve started allowing new meters because the plant is able to handle that need.

 

Anmargaret Warner. Photo by P. Vankevich

Anmargaret Warner. Photo by P. Vankevich

 

 

 

 

Anmargaret attended Ocracoke School till the eighth grade and graduated from Mercersburg Academy (PA).She made the Dean’s List at Wake Forrest and her degree is in English Literature and with minors in journalism and communications. This past year, she was accepted into the Fulbright English Teaching Assistant program. She taught English at the Balvantra y Mehta Vidya Bhawan Anguridevi Shersingh Memorial Academy in New Delhi, India.

Categories: General Information