Replacing old treatment equipment helps the environment, improves performance, saves money and helps the economy grow in Rome, N.Y.
An upgrade to the Rome (N.Y.) Wastewater Treatment Plant that allows for the treatment of specialized waste helped attract a new business to the city.
The upgrade also helped the plant slash electrical costs, while the new aeration equipment increased capacity and allowed operators to provide better treatment with less effort. And that is all good for the environment.
The upgrade was named Project of the Year by the American Public Works Association/Central New York. The plant has also been praised by the New York Water Environment Association and the state Department of Environmental Conservation.
The 35,000 residents of Rome are pleased, as well, because the $6.2 million turnkey project was self-funded. It will pay for itself through savings. In fact, the city expects to receive $8.6 million in savings and revenue enhancement over a 15-year performance contract with Johnson Controls, which developed and implemented the improvements.
Before the upgrade, the plant’s mechanical aerators were more than 30 years old and in dire need of replacement, according to Bill Baynes, chief operator at the 12 mgd plant. “Air capacity was a limiting factor in our ability to treat additional loading and even to meet our current permit requirements,” he says.
City officials already knew it would cost $1.2 million for custom parts to improve the existing equipment, and it would take about a year to have those parts fabricated. So they turned to Johnson Controls in February 2008. The company was in the midst of making energy efficiency improvements in many city buildings.
The Johnson Controls project team, which included CDM engineers, put together a plan for the wastewater plant that included fine-bubble aeration with single-stage centrifugal variable-vane blowers, dissolved oxygen controls, more efficient membrane diffusers, and instrumentation and control equipment.
The work was completed and the plant was back to full operation on Nov. 1, 2009. In the first month, the plant saved $11,500 in energy costs, right in line with the guaranteed savings of $111,000 per year under the 15-year performance contract. Annual energy savings are projected at 30 percent.
“We have ten aeration tanks in three basins and each now has its own Endress+Hauser dissolved oxygen probes,” explains Baynes. “The readings from the probes control the output of the variable-vane blowers (Turblex Inc. – A Division of Siemens Water Technologies).”
Turblex also supplied the automation instrumentation. “The system maintains a minimum air pressure and precise airflow and allows for the automatic flexing of the Aerostrip membrane diffusers (Eimco Water Technologies) to reduce fouling,” Baynes says.
“The amount of oxygen capacity is increased 50 percent going from mechanical aeration to the new blowers. We had plenty of capacity in our clarifiers and digesters, and solids handling was fine. Air was our limiting factor; it was what prevented us from treating any more volume or organic loading.”
He saw that limitation first-hand when the plant treated waste from the 200,000 people who attended the 1999 Woodstock reunion concert in Rome. “It was such strong waste that it almost shut down our system,” he recalls. “We could only treat about 20 gpm from the concert because of our aeration limitations. That was a heads-up for us.”
The plant’s SCADA system was modified to include trending of aeration process data. “It allows our operators to make adjustments to achieve greater energy savings and improve effluent quality,” says Baynes. “We also added baffles to improve the hydraulic distribution and detention time in the aeration basins.”
Baynes sees great improvement over the old plant, built in 1931 and upgraded several times. “The only way we could control the dissolved oxygen was to raise or lower the weir at the end of a line of tanks,” he says. “But we couldn’t control the individual tanks, so some tanks got too much air and some not enough.”
Flexibility for operators
The new system gives operators more control. “We can put the exact airflow and dissolved oxygen exactly where we want it,” Baynes says. “That allows us to better manipulate the plant biology and manage our activated sludge process.”
Operators find that such control helps them manage nitrification and denitrification, filament growth and energy use. Three containerized blowers, one 125 hp and two 250 hp, enable operators to set the airflow anywhere between 1,250 and 8,000 cfm to meet oxygen demand and provide better treatment.
“We used to draw from 240 to 270 amps with the mechanical aerators,” Baynes says. “That’s half of the total electrical use in the plant. Now we draw 75 to 85 amps.”
Operators can also monitor and trend the effects of different control strategies, monitor energy savings, and fine-tune the process. “Energy savings were certainly a benefit, but that’s just one part of what made this project work,” says Baynes. “We can really control the process and the biology of the plant like we never could before.”
Rome is the site of the former Griffiss Air Force Base, which was closed in the mid-1990s and is now a 3,500-acre business and technology park. “We want to be able to serve any business opportunities that might come along,” says Baynes.
The plant’s ability to treat high-strength waste helped influence the location of a cellulose ethanol demonstration plant that began operations in February 2009. “Hope-fully down the road, we’ll have other opportunities with businesses that can come into Rome because we have the capacity to treat their waste,” Baynes says.
The plant can now treat more high-strength leachate and septage from existing customers, such as a local landfill. Last year, the plant treated about 2.5 million gallons of leachate, and it will take at least 5 million gallons this year.
Baynes expects to see $156,000 in annualized operational savings in the first year alone from increased revenue and reduced maintenance costs. That is in addition to the energy savings. He estimates the plant is also avoiding $200,000 a year in capital costs by not repairing the old mechanical aerators. The plant may also receive energy rebates from the state — the status of the rebates will be determined after one year of operation.
Baynes believes the new features and automated controls in the new system will provide the flexibility to deal with unforeseen circumstances and provide plant capability to support future economic development.