No worries.” That’s how supervisor Jeff Totherow feels about his wastewater treatment plant when he’s not there.

It’s because of a competent and talented staff of Matt Smith, laboratory director; Bryan Gordon, maintenance director; Loarn Hinkle, lead operator; J.C. Davis, operator; and Jeff Turner and Martin Dixon, operator trainees.

Together they run the 5.0 mgd (design) Tullahoma (Tennessee) Wastewater Treatment Plant, which uses an intermittent cycle extended aeration system (ICEAS) to treat wastewater from a community of 19,000 about 75 miles southeast of Nashville. “They’ve got it together,” Totherow says. “They understand their responsibilities. I can sleep like a baby at night.”

Unique process

Constructed in the mid-1980s, the Tullahoma plant receives wastewater from a collection system with 160 miles of pipe, 42 lift stations, and more than 900 grinder pumps. The flow passes through center flow band screens (Hydro-Dyne) and is lifted by KWS screw pumps (Lakeside Equipment) to a pair of pre-air basins where grease balls are removed and the wastewater is freshened.

The ICEAS process provides complete treatment. It was the largest of its kind in the world and first in the United States when installed in 1985 by Austgen Biojet (now Xylem). It includes a pair of basins, each rated at 2.4 mgd.

Conventional sequencing batch reactors fill, aerate, settle, and draw. They require two or more basins or an equalization tank to receive flow during the settling or decant phase. The ICEAS, however, needs no diversion. It operates on a timed-based control system, allowing continuous flow during all phases of the cycle. The basins fill, aerate, decant and discharge once every two hours. Pre-react and main react zones are separated by a baffle; the pre-react zone can operate as a selector zone.

Totherow says the design has drawn visitors from all over the world who come to see how it works.

The system was upgraded in 1995 when 5,700 Series E fine bubble aerators (Sanitaire, a Xylem brand) replaced the original aeration system. At the same time, a 48 mgd retention pond was constructed to provide flow equalization during wet weather.

Power savings

In 2016, new Sulzer turbo blowers were installed to save on power costs. A new 250 kW natural gas backup generator (Kohler) was also added that year, and in 2017 the decanter drives were replaced. The plant changed its disinfection system as well, switching from gaseous chlorine to peracetic acid (PAA), supplied by PeroxyChem.

“PAA costs more,” Totherow says. “But we were able to use our existing chlorine contact basin and get rid of two very dangerous gases — chlorine and sulfur dioxide. Consequently, we no longer are subject to the Risk Management Plan regulations.”

PAA is a stronger oxidant than sodium hypochlorite and chlorine dioxide. Most of the disinfection occurs in the first minute of contact, and the acid decomposes quickly into acetic acid, oxygen and water. There is no need to neutralize it before discharge into the effluent channel and to Rock Creek.

The plant’s SCADA system was built in-house and uses the Survalent Technology platform.

Tullahoma practices cost-effective biosolids handling. Aerobic digestion stabilizes the material, which is then applied as a liquid on farm fields approved by the Tennessee Department of Environment and Conservation. The plant generates 2 million to 4 million gallons of biosolids a year, at 1% solids.

Top-tier performance

The plant is not only cost-effective; it’s compliant. For meeting discharge requirements regularly, Tullahoma received Operations Excellence Awards from the Kentucky-Tennessee Water Environment Association in 2014, 2017 and 2019. The plant received the association’s biosolids award in 2014.

The plant is essentially violation free. The key parameters of CBOD, TSS and ammonia are barely detectable in the effluent. Performance is a key to winning awards, but so is innovation, and Tullahoma has taken several steps to become more green.

“The turbo blowers use magnetic bearings, which don’t wear out and are very energy efficient,” Totherow says. “It’s new technology, and it has helped us cut energy costs by about $30,000 per year.”

The plant team has also installed LED lighting throughout the property. The elimination of chlorine and sulfur dioxide has removed disinfection byproducts and improved the safety of staff and neighbors. “With chlorine, we had a kill-zone of almost 2,000 people,” says Totherow.

Sharing the credit

Totherow was named Operator of the Year by the Tennessee Association of Utility Districts in 2017, but he declines to take credit: “It’s not about me. It’s about my team. Without them, it’s not possible.”

He calls lab director Smith one of the smartest clean water professionals in the field: “Matt is very bright, has a master’s degree in environmental science and natural resource conservation from the University of Tennessee at Chattanooga and joined us in 2010. I watched him the other day giving a tour to students. He taught them all about standard methods and CBOD.”

Totherow refers to maintenance director Gordon, on the staff since 2011, as the plant’s MacGyver. “He has lots of confidence. Piece by piece, he’s revamped the whole plant since 1995. He’s made changes to our bar screens and turbo blowers, getting ready for biological nutrient removal down the road.”

Operators Hinkle (24 years) and Davis (19 years) are loaded with experience. In Totherow’s view, there is no situation they haven’t encountered and can’t deal with. And he’s enthusiastic about the two trainees: “Jeff Turner also helps with our lift stations and has about two years on the job. This is Martin Dixon’s first year in the wastewater profession.”

Totherow is a good judge of talent because he has been there, and understands what it takes to be successful. Plant staff members often work by themselves. Operators need to be comfortable doing that, he says; he mastered that skill when he helped out on a dairy farm while in high school: “I milked cows by myself.”

After high school in 1970 he learned pipe fitting at the U.S. Department of Energy’s Y-12 National Security Complex in Oak Ridge, Tennessee. He then got an associate degree in data processing. He moved to Tullahoma in 1986 and two year later took a position at the wastewater treatment plant.

More change ahead

The Tullahoma plant isn’t finished making changes and improvements. The next challenge, Totherow says, is to take on new biological nutrient requirements. The improvements the staff has already made to the ICEAS system, changing the aerators and adding turbo blowers, will be a big help.

“BNR will be mandated by the state, and our town will keep growing,” he says. Based on its record, the Tullahoma plant will be up to the task. Totherow is proudest that the plant is better than when he started. It’s more compliant, cost-effective, safe and environmentally friendly. And, he could add, it’s worry-free.