Energy savings efforts earns award for Rifle sewer plant staff
Citizen Telegram Editor
Solar power supplies all the electrical needs – and then some – for the Rifle Regional Wastewater Treatment Plant in West Rifle, but it’s even more efficient now, thanks to the efforts of plant’s workers.
And those efforts, which resulted in a 20 percent reduction in electrical usage, were recently recognized with an award at the Garfield Clean Energy Innovation Awards in Rifle.
Garfield Clean Energy is a partnership of 10 local governments in Garfield County, and is the state’s first intergovernmental clean energy authority. CLEER: Clean Energy Economy for the Region, manages the programs and services of Garfield Clean Energy.
Thirty-one households, businesses and local governments were nominated for the second annual awards. Presenters handed out 18 awards in 12 categories, including the Active Energy Management award to plant operators Devin Jameson and Pat Lake and plant supervisor David Gallegos, who spent months experimenting with the plant’s equipment to drive down its energy use.
Sun Edison installed row after row of solar power arrays next to the plant several years ago, under an agreement with the city that locked in the power purchase price for 20 years, Lake said during a short tour of the plant on Monday, Nov. 4.
“They said we might get 60 or 70 percent of the power we need from the solar panels,” he added. “But we get up to 300 percent in the summer, so we’re putting the excess back into the grid, and we’re barely below 100 percent in the winter.”
Gallegos said CLEER contacted the plant last year, when they noticed the operation was hitting peak electrical demands through the daily data gathered at a monitoring web site.
“It just kind of snowballed since then,” he added. “I had a little doubt at first, but we just decided to take the dive and see what we could do.”
Gallegos compared the 2 million gallon capacity plant, which began operating in December 2009, to a new car.
“They want you to have all the extras,” he said.
Through trial and error, computer software tweaks and changes in operation times, Gallegos and his five-person staff “made changes in the way they operate the oxidation ditches, the interchange tanks and the clarifier tanks,” said Mary Wiener, energy efficiency program administrator for Holy Cross Energy, who presented the award. “They gradually dialed back the mechanical systems to trim electrical use while maintaining high-quality plant operations. The changes brought down overall electrical use and cut the plant’s demand spikes, which influences the price the city pays for electricity.”
“When we would run all three clarifiers, it would take a lot of time to clean them,” Gallegos said. “And we’re understaffed anyway.”
Lake said the staff soon learned, “You have to know your way around obstacles.”
“Sometimes we found we were headed in the totally wrong direction and had to start over,” he added.
“We were a little adventurous at times,” Gallegos said.
For example, the plant uses air-breathing bacteria to treat the wastewater. To keep the water aerated and oxygen levels up, there are three large oval-shaped “ditches,” with four sets of 50-horsepower electric paddle-wheels that push the water around the oval and aerate it as each paddle splashes into the water.
Before changes were made, all four sets of paddles ran to meet the oxygen level set point of 2.5 milligrams per liter. The paddles had to spin at full speed to get enough oxygen into the water, and factory settings and a computer software glitch prevented automatic paddle control from saving energy properly.
This year, staff experimented with control methods, debugged the software and tried new ways of operating the plant. The result was a lower oxygen level of 2 milligrams per liter, sometimes just two or three paddle sets are needed to meet the set point, those paddles spin slower and automatic control slows down or stops the paddle sets when possible, especially on cool days and at night.
“We have to adjust the bacteria settings and the system, depending on what’s in the water and what season it is,” Lake said.
Overall, the staff’s changes resulted in 10,000 to 20,000 kilowatt hours of electricity saved each month this summer, compared to the same months last year, according to CLEER figures, as well as a 44 kilowatt reduction in peak demand during June, July and August of this year compared to those three months last year.
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