An equipment failure led the staff at the Somersworth (New Hampshire) Wastewater Treatment Facility to make what they thought was a temporary procedural change. It worked so well and saved so much energy that they never fixed the problem device.

That kind of work helped the facility earn a 2019 Wastewater Treatment Plant Energy Efficiency Award from the New Hampshire Department of Environmental Services and NHSaves, a utility group that promotes energy conservation.

Somersworth was the state’s top-performing plant as measured by energy usage (0.62 kWh) per pound of BOD removed. The national benchmark for similar-sized activated sludge plants is 0.7 to 2.2 kWh per pound.

The Somersworth facility on the Salmon Falls River in southeast New Hampshire is in the early stages of a $13.7 million upgrade that will involve new energy-saving equipment, but the team earned the efficiency award without any recent equipment upgrades.

The plant’s last upgrade was completed in 2005 to meet new NPDES permit requirements. The aeration tanks were retrofitted to create anaerobic, anoxic and aeration zones for biological nutrient removal. The facility uses the modified University of Cape Town BNR system. The staff includes two operators, two maintenance mechanics, a chemist and a facility manager. The staff also operates and manages four lift stations and the industrial pretreatment program.  

Finding an energy hog

In 2016, the chlorine injection mixer at the front of the chlorine contact tank failed. Just upstream in the process is a filtration building with an overflow designed for use during unusually high flows. Instead of replacing the mixer, the staff decided to let some effluent overflow right into the disinfection chamber to agitate the water. It worked like a little waterfall.

“Doing that, we were able to get efficient mixing,” says Jamie Wood, chief operator. “A minute amount of our average daily flow agitated that line and allowed us to get the mixing we needed to meet our E. coli bacteria limit. So at that point, we decided to keep running it that way. It has worked for the past three years, and we’ve never had an issue.”

The change enabled the shutdown of a 3 hp motor that had run continuously.

“Winning this award was a lot of effort from the staff,” Wood says. “It means as a team we’re being recognized for constantly reviewing our operations and looking for areas where we can improve. It’s about not just getting creative, but also recognizing when opportunity presents itself. In this case, we had a failed piece of equipment, and we just took advantage of an opportunity and ran with it.”

Another example: “During the winter when we don’t receive septage, a lot of plants shut their pumps off but then fail to shut off the variable-frequency drives in the control room,” Wood says. “Those VFDs continue to run until spring without being used. We routinely inspect all motor control center panels to ensure unused ones are powered down and not wasting energy. In many plants, the VFDs may not be located in the same building as the pumps, so it’s easy to see why they may get missed.”

Efficiency behaviors

During design for the upcoming upgrade, an energy audit conducted by Process Energy Services of Londonderry identified areas for improving efficiency. One was adding extra controls to the boiler. Another was changing the lighting, from which Wood expects substantial savings. In the meantime, exterior lights have been placed on timers, routinely adjusted to turn them off during daylight.

“During the change from daylight savings time, I adjust those lights for that one hour,” Wood says. “It may not seem like much, but that’s an hour a day for five months. That adds up.”

Lights on clarifier and aeration tank walkways are operated with simple on/off switches and are used only as needed. At the exits of the basement pump gallery, Wood has placed signs that say, “Please turn off the lights. Thank you.” That saves more energy than might seem obvious, since those lights also activate an exhaust system.

The real benefit, though, is the impact of creating an energy-awareness culture. “It sounds cliché, but empowering our employees to make decisions and think like owners benefits the organization as a whole,” Wood says.

Wood thinks people rely too much on new equipment when looking to save energy. “There’s so much we can do just by identifying areas and reducing the energy used as the plant exists today,” Wood says. “A lot of times operators may look around and say, ‘I’ll wait until the upgrade comes.’”

Energy Champions

The Somersworth Wastewater Treatment Facility was honored by the state Department of Environmental Services and NHSaves, which for four years have helped treatment plants improve their energy efficiency. The agencies focused on wastewater treatment plants as the largest energy consumers in many municipalities. The effort started with a U.S. Department of Energy grant, and it continues with help from New Hampshire’s Clean Water State Revolving Fund.

In the award presentation, Somersworth was described as an Energy Champion because “Jamie Wood and his staff have done a phenomenal job with aging equipment (most 20-plus years old).” It noted Wood’s energy awareness, tracking of energy use, understanding of where energy goes and ability to “think outside the box and encourage his staff to do the same.”

The presentation concluded, “The Somersworth staff exemplifies the term ‘Energy Champion’ in their everyday work.”