Towering Above the Rest
On Ocracoke there are a lot of interesting things to see and experience. The beaches are serene, our lighthouse is the oldest operating – and definitely the cutest – lighthouse in North Carolina, Blackbeard spent his final days in the area known as Springer’s Point, sailors from the British Royal Navy killed during World War II are buried in the village, and descendants of the wild Banker ponies live in a pasture almost smack-dab in the middle of the island.
This week, the United Nations observed World Water Day, which is a good day to be thankful for Ocracoke's clean drinking water. It's not something to take for granted, so we want to show you and let you experience a lesser-known, interesting part of Ocracoke.
Seeing as how Ocracoke is an island surrounded by salt water, there are no obvious places providing fresh water for the island’s residents and visitors. Many wonder how water is supplied and if it’s safe to drink. One can tell people over and over and over again that the water is safe to drink; one could even go as far as to say our water is safe to drink because of reverse osmosis. But, what is reverse osmosis?
Before I hit you with some Bill Nye the Science Guy type knowledge, we should start at the beginning. David Tolson, who has worked for the water plant for almost 38 years, took me on a tour to show and describe how we get our water. The water system is run by the Ocracoke Sanitary District, which began operating in 1972. Five years later, the plant began using reverse osmosis technology, something that at the time was new and relatively unheard of. Since 1977, the plant has either been expanded or received upgrades seven times to accommodate the growing population of year-round residents and large amounts of visitors who come to the island each year.
Our first stop was to see one of the three well stations, all of which have large pumps and drills and are enclosed in sheds. The drills reach 620 feet below the surface, while the pumps have been placed 40 feet underground. These well stations, which are used one-at-a-time, bring up mineral water from the Castle Hayne aquifer, a large, underground aquifer that extends from eastern North Carolina.
Once the water is pumped up it goes through a pipeline and into a large filtering device. The pipe is visible, so we followed it – while David chanted “Follow the yellow brick road” – from the outdoor pump sheds into the plant, where I was able to see said filtering device. This large filter is the first step in the treatment process. Once the water passes through the filter, it goes through reverse osmosis.
So, what is reverse osmosis? Well, it’s the reverse of osmosis of course! Okay, time for me to hit you with the Bill Nye the Science Guy type knowledge I mentioned before. Osmosis, as described by Merriam-Webster, is: “the movement of a solvent (such as water) through a semi-permeable membrane (such as a living cell) into a solute of higher concentration (such as salt water) that tends to equalize the concentrations of the solute on the two sides of the membrane. Try saying all that in one breath! Basically, fresh water (less concentration) can go through a semi-permeable membrane and meet salt water (higher concentration) on the other side so the two meet, mix, and equalize on both sides of the membrane!
Now reverse osmosis is different. The official and very scientific definition of reverse osmosis (or RO) provided by Merriam-Webster is: the movement of freshwater through a semi-permeable membrane when pressure is applied to a solution (such as sea water) on one side of it. I’m fairly certain that when David Tolson started describing this process to me I had a bewildered look on my face, but he was kind enough to pump the brakes and explain. The water, which has been freshly pumped from the Castle Hayne aquifer, reaches the RO tubes after going through the initial filtration device. Once inside the RO tubes, tremendous pressure is applied which pushes the water through semi-permeable membranes inside the tubes. This pressure forces minerals and salts in the water to become separated, producing a more pure water. The more pure water is then diverted onto the next process. The water containing the separated minerals and salts goes through piping labeled “reject” so it gets rerouted and then emptied into the Pamlico Sound.
The Ocracoke water plant has nine individual RO systems, each of which contain twenty-one semi-permeable membranes. All of the nine RO units have their own individual monitors which track how well the water is being filtered in order to maintain a certain level of purification. If too many minerals are removed, the water would end up having a less-than-desirable taste, so a nice balance is maintained to keep the consumers happy. The filtering process and reverse osmosis-ing yields about 65% consumable water and about 35% reject water. But the water isn’t ready to be consumed yet.
[image6]Next, the pure water shoots through more pipes and goes through an aerator! What does the aerator do? It blows air through the water to separate it from gasses, and then the water trickles down through a series of balls causing it to cascade into a detention tank. The two detention tanks can each hold 200,000 gallons of water! Wowza! At the bottom of the detention tanks is a blower which is used to push those separated gasses up and away from the water. Have you ever sniffed a whiff of rotten-egg in the air? If you’ve ever smelled the gasses you may have a hard time believing this, but only one detention tank is to blame for the release of that not-so-sweet scent of sulfur we experience from time to time. Once reaching the detention tank with the tall sky-bound pipe, the gasses which were separated during aeration travel upward and out into the air through a vent. When these gasses are released, the smell of rotten eggs can sometimes be detected throughout the village. But residents and visitors won’t always smell the gasses because the plant doesn’t operate constantly 24 hours a day, seven days a week. Meters are installed throughout the water plant on various machines to track usage so the nice folks at the water plant are always able to keep our water supply well stocked. Wind strength and direction also play roles in where the sulfur can be smelled, and you’re more likely to smell it between May and September when there are more people visiting the island and there is a much greater demand for water.
With only a couple more steps, we are nearing the end of the water treatment process. The water in the detention tanks is fresh, but North Carolina regulations require certain chemical treatments. Minuscule amounts of these chemicals are added to our water supply, but both play important roles. Chlorine is added to prevent bacteria from growing, which keeps those consuming the water from getting infections. Zinc acts as a barrier, so it prevents lead and other metals from seeping into the water supply as it travels through piping.
The final step of the water treatment process happens after the chemicals are added. Towering above the village, sometimes even more visible than the Ocracoke Lighthouse, is the water tower! The light blue structure stands at 130 feet, and is quite noticeable with OCRACOKE painted in bold letters!
Ready-to-consume water is pumped into the elevated tank, and due to pressure is able to flow steadily throughout the village to supply homes and businesses with water. Our water tower’s elevated tank is equipped to hold 150,000 gallons of water and with the detention tanks capable of storing 400,000 gallons each, plus the large amount of available water in the Castle Hayne aquifer, we’re in good hands as far as the water supply goes.
So, now that we’ve been through the process of how the water is treated, I should tell you how all this stuff works: electricity! The whole water treatment plant runs off electricity, and electricity can be costly. During peak visitation months the water plant may have to pay around $8,000.00 a month to keep the plant operating. That’s quite a chunk of change! That’s also why year-round billing for residences, property owners, and businesses is based upon summertime usage. In order to provide year-round maintenance, purchase needed replacement parts, acquire equipment, complete any necessary building upgrades, and to ensure the plant operations continuously run smoothly, costs have to be covered year-round by everyone, whether or not they’re here or open year-round.
A reasonable question to be asked, then, knowing the plant runs off electricity is: what happens when we lose power? There are two things to keep in mind if you’re ever worried about the water plant not being able to operate or running out of water: the first thing is water is pumped, treated, and shot up to the elevated tank in preparation for what the demand could be at any given time of the year. During the peak visitation months the plant runs a lot more daily so there’s enough water and then some to go around. During the off-season months the water plant is still run daily, though it isn’t necessary to conduct the whole process multiple times a day like it is during the busier months since there aren’t nearly as many people here. The nice people who work at the plant are there to not only ensure our water is safe to consume, but that there’s plenty of it. So, if for some reason we full-on lose our sources of power, there is without a doubt extra water on reserve. The other, and possibly most crucial, thing to keep in mind is the diesel-powered generator that kicks on at the water plant when there is a power failure.
After Hurricane Arthur, which struck the Outer Banks in July of 2014, a scary rumor spread around that our water supply was on the verge of running out. If memory serves, we didn’t have power for three days, and it was early on during that time the rumor began. But as quickly as it started, the rumor ended. People started talking about the generator that was being used to keep the water plant running, thus quelling the fears of residents and visitors who stayed. And our water supply was never compromised!
So, getting back to the elevated water tank; water is released from the tank and snakes around the village, through individual water meters, and into our residences and businesses! When the water in the elevated tank is depleted to a certain level, a sensor reacts and alerts those friendly folks at the plant that more water needs to be sent up! And so water is then sent from the detention tanks to be treated with chemicals, and after will be pumped into the water tower. When the water in the detention tanks needs to be refilled, more sensors alert the nice folks at the plant to start a well pump to bring up water from the aquifer, and the whole treatment process begins again! Thanks to David Tolson, Dave Frum, Robbie Lewis, Earl Gaskins, Marcus Lawson, and Janie Garrish for keeping the clean water flowing!
Stay hydrated, Ocracoke!
Wondering how the good people of Ocracoke got fresh drinking water before the water plant was built? Find out all about cisterns on the island in this story by Philip Howard.
