When a pilot test showed that a new post-aeration system was increasing dissolved oxygen by 70 percent while using 75 percent less power and liquid oxygen, the team at the Paul R. Noland Wastewater Treatment Plant knew they had found something they wanted. Run by CH2M HILL, the plant in Fayetteville, Ark., became the first to use a new technology for polishing effluent — a Supersaturated Dissolved Oxygen Injector.
Called SDOX by its inventor, BlueInGreen of Fayetteville, the technology was developed with funding from the National Science Foundation and private equity investors. “I met them in 2006,” says Duyen Tran, project manager at the plant. “The founders are professors at the University of Arkansas. It sounded interesting, so we set up a live trial run. We tested it for a month and it looked very beneficial for our process.”
The test indicated potential savings of $15,000 per year, so the plant installed it in late 2007. “We now realize savings of more than twice that amount per year, so it’s been very good for us,” Tran adds. “At the time, we thought we’d get payback in about five years. We actually had the system paid for in less than three years.”
The pilot helped the SDOX win the 2010 Innovative Technology Award from the Water Environment Federation.
That’s just one of the many things the plant has done to save money and reduce environmental impact. For instance, improved SCADA monitoring of lift stations and more efficient driving routes reduced truck travel by 6,100 miles, saving 436 gallons of fuel and 9,069 pounds of CO2 emissions annually.
The plant has also maintained a Running Register of Sustainability that encourages suggestions from the staff. Resulting projects include:
• Increased lighting efficiency
• Solar drying of biosolids
• Automated control of aeration
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• Pedal-powered and electric vehicles for in-plant transportation
First of its kind
The SDOX technology has reduced the use of liquid oxygen at the plant by 2.8 million cubic feet a year, according to operations manager Tim Luther. “It uses new oxygenation technology that restricts oxygen loss to the atmosphere so that nearly 100 percent of the oxygen fed to the system is dissolved,” he says. “It uses less oxygen and power, saves money, and is much more environmentally friendly. That is sustainability.”
The oxygen is supersaturated into solution under pressure, and the solution is fed into the treated effluent for polishing, enabling more efficient oxygen transfer. With no degassing taking place, all of the dissolved oxygen is available for the natural removal of residual volatile organic compounds (VOCs) and other pollutants.
Delivering up to 350 mg/l of oxygen, according to BlueInGreen, the system can be used for odor control in facilities such as force mains, for supplemental oxygenation in other plant processes, for lake and reservoir oxygenation, and at spill sites in rivers and streams to provide oxygen to prevent fish kills.
Fayetteville’s 12.6 mgd A2/O biological nutrient removal (BNR) treatment plant is also testing another BlueInGreen invention called HyDOZ. That unit, already proven in small-scale tests, is in its first large-scale pilot test. “Using the same principle as supersaturated oxygen, it uses supersaturated ozone to help disinfect wastewater,” says Tran. “The added benefit could be the removal of emerging pollutants like pharmaceuticals and volatile compounds.”
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The staff is encouraged to suggest projects that are evaluated and tracked by a spreadsheet tool called the Running Register of Sustainability. “It uses weighted criteria to determine which projects will give us the best benefits: environmental, financial, and social,” says laboratory director and sustainability champion Bruce Richart.
The tool was designed by the CH2M HILL Sustainable Solutions Business Group. The ideas come in an annual plantwide brainstorming session. “We started out in 2007 with some of the easier projects, like a recycling program and eliminating polystyrene cups and bottled water,” says Richart. “The best ideas come from the people who are closest to the process.”
Many of the projects, like lighting efficiency, require no capital cost. “We went out one evening and looked around the facility,” says Richart. “We were able to turn off some breakers and switches. That reduced the exterior lighting by 42 percent while still maintaining safety and security.” It also reduced sky glow from the plant.
Another noncapital idea improved the treatment process. “One of the biggest ones involved the aeration basins,” notes Luther. “We installed automatic controls so the aerators dynamically switch from high-speed to low-speed to maintain a certain level of dissolved oxygen.” That has saved an estimated $13,000 per year in electricity and labor.
Other projects are extremely simple. One suggestion was to acquire zero-emission transportation — an industrial tricycle — for staff to get around the site. “We purchased one in early 2008 to see if the staff would use it,” says Richart. “A good percentage of the staff like it, and you get the cardiovascular benefit.”
It eliminated a gasoline-powered utility cart, and that led to replacement of another gas-powered cart with an electric model this year, saving 161 gallons of gasoline in the first six months. Beyond the sustainability register, the plant tracks many indicators of sustainability including energy use, transportation, chemical use, potable water consumption, effluent reuse, recycling, and community involvement.
One of the first things identified in the Running Register of Sustainability was biosolids drying. After a few years of planning, six Parkson Thermo-System active solar biosolids dryers were installed in spring 2011. The 42- by 204-foot enclosures use the sun for 95 percent of the energy needed to dry biosolids. Four semi-trailers of wet biosolids are reduced to less than one trailer, reducing the amount going to the landfill.
“In the first six weeks, we had diverted 61 tons of biosolids and saved 8,900 gallons of diesel fuel in transportation,” says Luther. That saved $63,000, and the plant now saves about $1,000 a day. A thermal gas dryer from Fenton was added late in the year, allowing the plant to produce Class A biosolids for beneficial reuse.
A related idea from an employee has made the transportation more cost-effective. “It’s hard to get the biosolids out of the back of the truck when you empty it,” says Luther. “We were purchasing vegetable oil to coat the box. One of the staff members had the idea of purchasing used oil from a food processing facility. What used to cost $7 a gallon now costs $1.25.”
Fayetteville is in the northwest corner of Arkansas, in the Boston Mountains of the Ozark range, just outside the Ozark National Forest. A 5.3-acre meadow restoration led to replacement of invasive plants with native wildflowers and grasses.
A larger effort was the 46-acre Woolsey Wet Prairie Sanctuary, now a popular tourist attraction and outdoor classroom. The project restored the area to native plants and habitat that attracts a diverse mix of wildlife.
In addition, an acre of grass in front of the plant has been replaced by a xeriscape garden that needs less watering. The staff at the Paul R. Noland plant has proven that a focus on sustainability doesn’t have to mean large capital expenditures to achieve big improvements.