There was supposed to be a three-month window. It didn’t materialize.

Instead, the old water filtration plant in Hendersonville, Tennessee, closed at 10:09 a.m., and at the same time, a new one started up 1,000 feet away. It was Aug. 26, during the peak demand season.

“Needless to say it was an interesting day,” says John Wunner, water treatment superintendent in Hendersonville, about 18 miles from downtown Nashville. “The new plant was ready to open, but usually plant operators would prefer doing it in winter when demand is lower,”

What opened on that day was one of the most advanced water filtration plants anywhere, certainly the most advanced in Tennessee. It’s advanced because Tom Atchley, general manager, and the Board of Commissioners looked at the future of regulations and customer demand. The drought of 2007 played a part, too.

“The drought gave us a chance to rethink where we wanted to go,” Wunner says. The city’s population increased by 9 percent from 2010 to 2015 (it’s 53,500 today), and the real estate market is hot. “We’ve almost reached the limit for residential development,” Wunner says.

Best technology

The district faced a choice: refurbish the old 8 mgd conventional filtration plant at a cost of several million dollars or invest in a visionary plant to meet the community’s needs for years, comply with stricter regulations in the future, and provide superior water quality.

The plant sits beside a flowage of the Cumberland River, source of the city’s drinking water. On the way to the Ohio River, the Cumberland River drains about 18,000 square miles in Tennessee and Kentucky, home to 2.5 million people. They worked closely with neighbors, who agreed to accept a new plant on the same site as the old one, which was demolished last summer.

From the outside, the plant looks much like a modern suburban house, but on a larger scale. On the inside, it’s more interesting. The intake lies 210 feet offshore in about 17 feet of water. A 36-inch pipe brings water to the plant.

Raw water first reaches the dissolved air flotation cells (Leopold - a Xylem Brand). There is no first-step chlorination, only the addition of 48 percent alum for coagulation. Water flows next to microfiltration membranes (Pall Water) and then to the granular activated carbon beds (Calgon Carbon Corporation) and a UV array (Calgon Carbon Corporation) for polishing. The last step is the addition of residual chlorine for storage and AquaPure 3655, a proprietary blend of orthophosphates and polyphosphates from Brenntag North America, to inhibit corrosion.  

Wunner has no trouble declaring his plant the most advanced in Tennessee. “Other municipalities cannot employ the technologies we have because they do not have the money or the resources,” he says. Putting these technologies together in this way was the suggestion of the engineering company Water Management. The firm recommended and designed the DAF system that, along with the Pall Water membranes, were costly upfront.

When the new plant went into operation, it was a $27 million investment in the future. But it was the commissioners who decided on this course, and they did it to prepare for the future. Consider, Wunner says, that the U.S. Environmental Protection Agency is working on rules about pharmaceuticals in the water supply and on disinfection byproducts. Installing microfiltration is a proactive investment that secures Hendersonville’s ability to meet future regulations.

“We can take out everything we’re supposed to take out, and as regulations change, we’ll be able to remove inorganics or volatiles for years to come,” Wunner says. The membranes do most of that work — all of it during the winter months when demand and the organic load are low.

From April to October, the plant uses the activated carbon beds and UV lamps to polish the water coming out of the membranes. The UV lamps are costly to operate, so Wunner is careful with their use. The activated carbon beds are useful for other issues. Like lakes in many parts of the country, the Cumberland River Basin is subject to algae blooms and spikes; and the carbon removes the dirty, earthy odor that algae imparts to water.

Raw water turbidity is not a great problem for the Hendersonville plant, even though it sits on a river. The intake draws from Old Hickory Lake, and it and the plant are situated just above a dam. Most of the flowage lies upstream of the intake, so the flowage acts as a huge settling basin that intercepts much of the sediment washed into the water by rains farther upstream. It is rare that turbidity exceeds 5 or 10 NTU, Wunner says.

A great team

A building with advanced equipment is nothing special without quality people to run it. That’s why the plant has a wall of fame for operators. On the wall are engraved plaques showing the years of service of each person, copies of their certifications, and awards given to the utility. “I have the best job in the utility district because of the crew I have serving with me,” says Wunner, who holds a Grade 4 water treatment operator license. His team includes:

• Jason Chalfont, supervisor and Grade 4 operator
• Michael Burlison, Kenny Bain, Steven Reppel, Erik Baeder and Scott Jones — Grade 4 operators; Charles Stone and David Nanney — Grade 3 operators
• Kristofer Stoner, operator trainee

“Half of the crew members are over 50 and have been with us for more than a decade,” Wunner says. “We’re fortunate to have longevity because Grade 4 operators are hard to find and retain. What is even more impressive, we have created a mindset where excellence is not considered above average. We want to keep that culture because it maintains public confidence in us.”

Wunner himself is a testament to the attractions of a water job in Hendersonville. He started working as an auditor in New York and still carries the accent of a native of that city. When he moved to Tennessee, he worked in retail and at Nashville’s airport. At age 35, he was open to opportunities and saw an ad for a water treatment operator on the midnight shift. “It sounded like a cool and interesting field to be in, and I could keep my other job,” Wunner says.

He started with Hendersonville in 1996 and became superintendent in 2006. He never left his old skills behind. They served him well, he says, because auditing requires looking at systems and people, forming profiles of them, and making informed judgments based on what they’re doing and what they will do.

No pain in rain

For most water plants, sitting next to a large river means being wary of rain upstream and the sediments it flushes from the land. “Rain has no effect on us,” Wunner says. The plant has been granted a waiver that allows reduced testing frequency for trihalomethanes and haloacetic acids.

The plant process has another benefit: less sludge. The old plant was sending 12.5 million gallons to a Nashville wastewater treatment facility; the new one produces about 3.5 million gallons — 72 percent less. “You know what that equates to when you get charged by the gallon,” Wunner says.

The plant has public support because Wunner makes a point of cultivating it: “Making the public aware of a finite commodity is the best way to protect it.” The staff gives tours upon request to anyone from children younger than 3 years old and Girl Scout troops to students on high school and college field trips.

Staying secure

Public knowledge also helps keep the water plant secure not just from acts of terrorism, but also from simple acts of mischief that could put the water supply at risk. “In this age, when people want to show off by putting videos of themselves on the internet, there is a fine line between pranks and damage,” Wunner says. “It costs thousands of dollars to clean a storage tank, and to me, that is no longer a prank.”

Plant operators have iPad tablets that allow them to see the status of the system and issue commands, but they don’t work outside the building. “Can I operate the plant from my house? No,” Wunner says. “Personally, I wouldn’t want to because I’m the type who likes to come out from behind my desk. I like to walk my own facility and see what is happening.”

Built for the long run

All the planning and work has given Hendersonville a water plant that will fill the community’s needs for many years and is positioned to meet almost any standard regulators may impose. The plant is rated for 10 mgd but could be expanded to 12 mgd if the need arises. The district is also building a 1.5-million-gallon storage tank to expand capacity and reduce the number of low-pressure zones. And cross connections would enable the city to draw water from the nearby water utility in case of a drought.

“This water plant is a product and a testament to all of the people in the Hendersonville Utility District who had the vision and foresight to make it happen years before our water resources would begin to cause problems for our customers,” Wunner says. “I have a wonderful crew of operators who make this all happen. Awards are very nice, but they come because of the work of all those people, and I’m just lucky to be a part of it.”

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Bottled up

When Hendersonville built its new water filtration plant, it included machinery from Norland International to produce bottled water — not for profit but for two other purposes.

One is to provide publicity for the operation, says John Wunner, plant superintendent. The bottles come out in groups of eight and are shrink-wrapped in packages of 24 for giving to community groups or people taking tours. The bottling takes place behind a large window so tour groups can watch.

The other purpose is to provide water in case of a civil disaster. Hendersonville doesn’t have the equipment to supply the entire community in that event, but the operators can deliver 3,500 unlabeled bottles per hour. “That would be for an extreme emergency,” Wunner says.

A typical bottling run produces 1,200 to 1,800 bottles per hour. Five to six operators run the equipment as it disinfects, fills, caps and labels the bottles and dates the production run. Bottling is typically done one day each week when everyone is scheduled to work. The bottling equipment runs twice a month.

The equipment cost $250,000. And because the water is not bottled for resale, it does not fall under rules of the federal Food and Drug Administration.