Tim Mills operates the town of Bethel, Vermont, wastewater treatment plant all by himself. He’s up early to be at the plant by 6 a.m. He returns each night around 7 o’clock to check on things before he heads to bed.

He takes vacations in his RV just eight miles from town so he can maintain close contact with the plant. He’s been doing that since 1987, and he wouldn’t have it any other way. “It’s not a job, it’s a lifestyle,” says Mills, winner of the 2016 Operator Excellence – Wastewater award from the Green Mountain Water Environment Association. “You find out who you really are. There’s nobody else here to let you down. It’s just you.”

Keeping it clear

The Bethel treatment plant came online in 1987, the year the town hired Mills to operate it. The design flow is 115,000 gpd; an oxidation ditch process yields crystal-clear effluent that’s discharged to Vermont’s White River.

The oval-shaped ditch (75 feet long by 20 feet wide by 7 feet deep) is equipped with a fin-type rotor that aerates and mixes the contents. Two circular clarifiers follow, and the effluent is UV disinfected. BOD and TSS removal averages 98 to 99 percent.

Waste activated sludge is stored on site in an aerobic digester that’s emptied twice a year. The digested material is hauled as a liquid to the Montpelier Wastewater Treatment Plant about half an hour away; it is dewatered there and sent to a landfill.

For many years, the biosolids were applied by injection on farm fields, but the sites were in an area that the state Department of Fish and Wildlife is returning to its original condition. Hauling costs are about $25,000 a year — about 10 percent more than it cost to land-apply. “That’s a bargain when you consider the time saved, plus not having to deal with traffic or liability with the equipment on the road,” Mills says.

Flying solo

As the sole operator, Mills has had to be creative and resourceful. When the state imposed effluent nitrogen requirements a few years ago, Mills put on his thinking cap and went to work on his oxidation ditch. “By controlling the speed of the rotor, we’ve been able to achieve nitrification-denitrification biologically,” he says. “We create an anoxic zone in the ditch.”

That is accomplished by increasing the mixed liquor suspended solids level and using the inverter on the rotor to slow it down so that oxygen levels drop to as low at 0.1 mg/L through the last one-fourth of the ditch. “It gets just enough oxygen to make it around the bend” before encountering the rotor again, Mills says.

Temperature is another factor that makes it difficult to maintain the nitrification-denitrification process. “In the fall, when the wastewater temperature drops and we hit about 60 degrees F, we increase the MLSS load,” Mills says. “It doesn’t end up being a complete nitrification-denitrification process, but it’s close enough to maintain reasonably low nitrogen levels. We run with a heavy MLSS throughout the cold weather, and we can easily meet our limit of less than 11 pounds of nitrogen a day, even in January and February.”

Diverse experience

Adjusting the rotor system is just one of many steps Mills has taken to fix things and improve operations — and that goes to his background. After high school and a brief stint in landscaping, he earned his first operator’s license while working at treatment plants in Plainfield and Randolph, Vermont. He worked up to a Grade 3 at Randolph, but moved on when he couldn’t see an opportunity to become chief operator. He moved to Bethel as the head man when the town opened its new plant and has been there ever since.

“I bought a house here, raised a family and we are very happy,” he says. “If I need someone to lend a hand, I have a gentleman on the town road crew with a Grade 1 operator’s license. I can call on him to help out.”

Town Manager Keith Arlund says, “I have a great deal of confidence in Tim. He is very professional and has a high level of mechanical skills.” The skills come in handy. Mills used them recently when a small fire burned out the control panel for the UV disinfection system.

“The original equipment manufacturer had gone out of business,” he recalls. “I had lost all my controls, but I thought I could put it back together my way. I did some UV spectrum analysis with some stronger ballasts and found they produced a stronger light.” Mills installed them, added an on/off switch, and saved the town about $100,000 with his home-built unit.

“I did one unit, then the other,” he says. “I check the lamps every morning and everybody’s up and running and happy. We have no more electronics to be fussy with.”

Boosting reliability

His Yankee ingenuity also helped solve a maintenance problem with the rotor. “During winter freeze-ups, ice tended to smash the fins on the rotor,” Mills says. “The estimate was $200 a fin, plus a $1,200 setup fee at the factory. Twelve fins are bolted together to form one ring of fins around the rotor, which has 10 rings.

“I bought 12 strips of steel (10 inches long, a quarter-inch thick and 4 inches wide) and hired a local welder,” Mills says. “We unbolted the original fins and welded new strips in their place around the rotor barrel. We haven’t lost a tooth since.”

In another case of do-it-yourself, Mills replaced the belts on the rotor drive units with chain and sprocket mechanisms. “We were going through drive units way too frequently,” he says. “If the belts got too tight, we’d burn the bearing; too loose, and we’d burn the belt.” Now, the gear drive works fine, and the plant saves the $1,500 it spent every eight to 12 months on new belts, bearings and oil: “We put a new chain on every 2 to 3 months at a marginal cost.”

Mills also got rid of the belts on the sludge pumps, replacing the original units with direct-drive electric motors controlled by inverters. “We used to use so much oil around the plant that I’d get an oil infection,” he jokes. “We’ve gotten rid of 90 percent of the oil, and that’s another significant saving.”  

Taking on more

As if the treatment works didn’t put enough on his plate, Mills is in charge of the town’s collections system and four pump stations. He deals with the consequences of residents’ flush-it-and-forget-it syndrome. “People don’t understand what not to flush,” he says. He’s committed to a clean system that generates no emergencies.

“We contract for a Vactor Manufacturing truck to clean out all wet wells and sags every fall, just before winter. Our system is only 30 years old, but we also clean one mainline section of the system each year. It’s an ounce of prevention.” The town is fortunate to be home base for Green Mountain Pipeline Services, which cleans and lines pipes all over the Northeast: “They usually return home on Thursdays and are available for jobs locally on Fridays.”

The four pump stations create another set of issues. The system doesn’t flow by gravity — it’s 100 percent pumping. Electrical failures are the biggest problem. The two main pumping stations have 100 kW emergency diesel generators (Yankee) and so does the treatment plant.

The two main pump stations are also connected to the plant through radio communication, which alerts Mills of alarm by way of a pager. Always on the alert for improvements, Mills has changed the alarm systems in the pump stations.

“There are four floats in the wet wells of the pump stations,” he says. “The floats are set from lowest to highest: pump shut-off, lead pump, alarm, and finally lag pump. That way, I get alerted if the lead pump can’t keep up or is broken down and the lag pump is needed in order to keep up. That saves us a lot of trouble in the end. In my little world, that’s huge.”

Sights and sounds

Like most solo operators, Mills has learned to look and listen to the treatment plant. “I can tell how it’s doing by the way it looks — the mixed liquor color in the oxidation ditch, the amount of algae on the walls of the ditch, and the effluent,” he says. “There’s a difference between clear effluent and polished effluent. Polished effluent actually glistens. It sparkles when the sun shines through it. You’re not going to make it any better.”

That’s important to Mills, who loves to fish. “I’m intrigued by the White River running past our plant,” he says. “When the plant’s running good, I feel that I am doing my part in maintaining the river and this job is something worth doing.

“I can tell how the plant is doing by the way it sounds. When I come back between 7 and 9 at night, I listen to it. It’s hard to explain. You end up being intuitive by what you hear.”

Mills finds a lot to like about working alone, even though he admits that being chief operator puts the bulls-eye on his back. “You’re the guy whose name is on the final report. Your name is the one in the newspaper,” he notes. “But it means everything to me, and I can’t emphasize that enough. I think the world of the community I work for and live in.”

The 2016 award from the Green Mountain Water Environment Association “came out of left field,” Mills says. “I had no idea. An official with the Vermont Department of Environmental Conservation nominated me. The town manager called and asked what I was doing on an upcoming date and told me to make space on my calendar. Two weeks later, he told me that I would be receiving the award and we were going to attend the presentation together.

“The nominator stated during the presentation that he had learned a great deal about wastewater from his work with me over the years,” says Mills. “That was the best compliment I’ve ever received.”

Turnover of veteran personnel in local government agencies is another issue: As they retire, they take important hands-on knowledge with them. Younger staff members coming out of school have the book learning but lack the field experience of running a treatment plant.

“Everything is not just black or white,” Mills says. “There are a lot of shades of gray, and, as we all know, it really doesn’t matter what the book says. Bacteria can’t read.”

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Future challenges

As resourceful and successful as he has been, Tim Mills realizes the profession is not without challenges. “What worries me most is having something happen to the plant that I can’t control,” he says. “We did have some episodes in early 2000s when our UV unit wasn’t getting penetration. It all depends on what’s getting flushed down the collections system.”

He also shares the concerns of wastewater professionals across the land about unfunded mandates: “I worry about new regulations coming down but no funding to support them.”