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Let the Bugs Do the Work
A one-of-a-kind facility at Albany International Airport treats plane de-icing fluid wastewater to drinking water standards, saves a pile of money, and even generates its own energy
By Tom Gibson
In
the late 1980s, Albany International Airport (AIA) faced a consent order
from the New York State Department of Environmental Conservation that
threatened to shut it down. Airport officials were required to stop discharging
plane de-icing fluid into nearby Shaker Creek. Wastewater generated during
aircraft de-icing and defrosting operations would run off through the
airport's storm drainage system and into the creek.
AIA hired an engineering firm, Clough, Harbour and Associates, to find a solution. The only practical one was to capture and contain the wastewater and send it to the Albany sewage treatment plant. Shawn Veltman, a partner with Clough, Harbour at the time, recalls, "It was an expensive option but the only viable one given the timeframe available."
With the threat abated, the airport could've stayed with the status quo, accepting the system as good enough to meet regulations. But through a joint effort spearheaded by Veltman between disparate groups of academic, government, and private sector people, they implemented a more advanced system that ranks as the first and only of its kind in the world. The Storm Water Recovery and Treatment Facility uses anaerobic microorganisms in a unique application to digest propylene glycol, a key ingredient in de-icing fluid. In addition to saving three quarters of a million dollars a year, the system has garnered awards and attracted the attention of airports around the world struggling with the same problem.
After stopping at an observation area and watching a few planes take off and land, I park at the airport's main terminal and stroll through the modern brick and glass structure. It buzzes with activity late in the morning. A mid-size facility, AIA serves the capital region of New York and surrounding areas. With 14 carriers and an average of 135 daily arrivals and departures, it ranks as the 70th largest airport in the country.
I
later meet with Steve Iachetta, airport planner at AIA, who tells me,
"De-icing is a big part of the cost of aircraft operations."
Crews spray deicing fluid on aircraft wings to remove snow, ice, and frost
and prevent them from forming. These elements can alter the shape of a
wing's airfoil section and its surface flow characteristics, causing a
loss of lift that can prevent a plane from taking off or cause it to crash
if ice develops in flight. At AIA, the de-icing season runs October through
May. Using a mixture of half propylene glycol and half warm water, they
consume 150,000 gallons of propylene glycol in a season and generate 30
million gallons of glycol wastewater.
Actually a sugar, propylene glycol sees use in hundreds of consumer items
such foods, beverages, and cosmetics. But it can contaminate drinking
water and disrupt aquatic life when it gets into bodies of water. AIA
must maintain a propylene glycol concentration of less than a part per
million in Shaker Creek -- one of the strictest limits in the country
-- because it flows into the Mohawk River, a drinking water source for
nearby towns.
A Costly Way to Go
AIA installed a trench drain collection system around the gate area
of the airport, and propylene glycol wastewater is captured in it and
pumped to a storage tank and two lagoons. The state originally mandated
that they transport the wastewater to a large sewage treatment plant on
the Hudson River at North Albany 12 miles away. The first year, they trucked
wastewater to the plant as they completed construction on a pipeline.
On its way to North Albany, wastewater passed through the town of Colonie's
sewer plant, which tacked on additional charges. Iachetta says, "There
were conveyance fees, treatment costs, and pumping charges that brought
it to over a million dollars a year in operations costs."
Typical sewage treatment plants use an aerobic process, in which naturally-occuring bacteria work in the presence of oxygen to convert organic matter to carbon dioxide and sludge. Sim Komisar, professor of environmental and energy engineering at Rensselaer Polytechnic Institute (RPI) states, "If glycol goes to a regular wastewater plant along with domestic sewage, it'll degrade, but it's just so strong it'll blow the plant out." De-icing fluid stormwater has a high oxygen demand, meaning it takes large quantities of oxygen to oxidize it and break it down to harmless elements. It also takes large amounts of time for the bacteria to work. At the Albany sewage treatment plant, the de-icing wastewater generated over a four or five month period had to be metered in over a 12-month treatment year. This required storing wastewater in lagoons at the airport year round and eight million gallons of storage space.
When
Clough, Harbour and Associates (CHA), a multi-discipline firm based in
Albany, did their initial work, they evaluated several long-term options
for the airport to consider as time allowed. One was anaerobic treatment,
which involves different forms of bacteria treating wastewater in an oxygen-free
environment.
This set Shawn Veltman on a mission. He had an undergraduate degree in civil and environmental engineering from Clarkson University and a master's in environmental engineering. Veltman says, "At that point, I had an interest in pursuing the anaerobic option, and I decided to go back and get my Ph.D. at the University of Massachusetts." He approached Mike Switzenbaum at UMass, whom he knew. Switzenbaum had been a professor at Clarkson when Veltman was there, and he knew Switzenbaum was an expert in anaerobic treatment. "I told him I thought it would be useful to look into the anaerobic treatment of aircraft deicing fluids because there was a big issue at Albany, and obviously it was becoming a big issue at other airports. It had not been demonstrated you could handle that kind of waste stream with an anaerobic type process."
Veltman wrote a proposal to the New York State Energy Research and Development Authority (NYSERDA) to seek funding for a plan involving RPI, UMass, and CHA, and he got financial support to do a technology assessment. "That was the framework for my Ph.D.," he relates. He brought a team together and convinced a number of people it was worth doing.
Komisar got involved in the project because he had an interest in anaerobic treatment systems, and one of his students had looked into anaerobic treatment. He recalls, "We were actually playing with a system for using anaerobic treatment for de-icing fluid a couple years before the project got off the ground. So we already had some stuff ongoing in the lab."
Veltman points out that NYSERDA not only wanted to see new ideas but to see them commercialized. He approached a number of companies that had proprietary reactor designs and ran into a company called EFX Systems based in Lansing, Michigan. EFX is a subsidiary of Ecolotrol in Westbury, New York, which originally developed fluidized bed technology for wastewater treatment.
This technology was developed by researchers at Manhattan College and the New York State Department of Environmental Conservation in the late 1960s as a means of removing nitrogen from processes. They obtained an old trickling filter plant, which trickles sewage over rocks to treat it, with bacteria adhering to the rocks. They determined that if they used sand instead of rocks, it would would increase the bacteria-holding surface area by an order of magnitude and yield higher reaction rates.
Ecolotrol
formed out of this concept in 1972. Roger Owens, a graduate student at
Manhattan College at the time, joined Ecolotrol at the start and became
one of its owners. He has a B.S. in civil engineering, a master's in environmental
engineering, and an MBA. EFX Systems provides equipment, engineering services,
and field support for handling difficult industrial effluent and groundwater
treatment problems. The company works closely with William F. Mitchell
& Associates, an engineering firm in Wilton, Connecticut.
Veltman reports, "We initially did some bench scale work to demonstrate that the material could be degraded anaerobically." Then he persuaded EFX Systems to provide a skid-mounted generic fluidized bed reactor, actually a 20-foot tall cylinder with associated pumps and control equipment, for a pilot test. Komisar recalls, "That made our lives really easy." They identified a site on the airport property and erected a temporary building for the reactor. He adds, "The same piece of technology EFX gave us had previously been doing an aerobic system, where air was added. We turned off the air addition, and the system becomes anaerobic."
New Way to Apply an Old Idea
Komisar points out that "the use of anaerobic technology isn't
a novel idea. This has been around since people have been burying stuff
in the ground. That's what landfills produce. It's the same basic idea,
just that using it for this purpose, and especially at the strength of
the wastewater we had to deal with, presented challenges." The pilot
plant worked well, as the anaerobic process was able to reduce the oxygen
demands to levels typically seen by sewage treatment plants.
The system Veltman and company developed uses an anaerobic fluidized bed reactor (AFBR). In this, water is pumped upwards through a bed of granular activated carbon -- small pieces with irregular surfaces -- at a velocity sufficient to fluidize, or suspend, the media. Treatment of organic carbon in the water comes via a thin film of microorganisms that grows and coats each particle, providing a vast surface area for biological growth. The bugs occur naturally in sediment, peat bogs, cattle intestines, and even brewer's yeast. As the bacteria degrades organics in the deicing fluid (primarily glycols), they convert to harmless end-products such as methane, carbon dioxide and new biomass.
Treating wastes anaerobically offers several advantages. It requires no oxygen through aeration, and it takes much less energy to operate. It produces less than 10 percent of the sludge of an aerobic process. Because the biological process is contained in a sealed reactor, odors are eliminated.
Although these advantages have been well known for many years, the application of anaerobic treatment hasn't caught on due to the widespread impression that anaerobic systems are unreliable, difficult to control, and require excessive residence times and huge reactors. "But," Komisar says, "that's changed a lot. If you have some idea of the science of what's going on inside the reactor, if you don't just treat it like a black box, if you have some sense of what the organisms are doing, it's not that hard a technology to run and control."
With the success of the pilot test, the team proceeded with designing a fullscale anaerobic system for the airport. CHA Tech Services (CHATS), Clough, Harbour & Associates' construction management arm, performed a comprehensive investigation of de-icing chemical usage at AIA and then worked with EFX Systems to design and construct a facility to house the treatment process. CHATS handled civil engineering work such as foundations and the building on a design-build basis, while EFX provided the equipment. Upon completion, operation began with the 1998-99 de-icing season.
Iachetta took me on a drive around the airport complex to the treatment facility for a tour. On a warm September day, we enter the building housing the anaerobic process, and plant operator Mark Sober starts by saying, "It's nice and quiet in here." The loud hum of several pumps running normally permeates the air in winter. A sea of pumps, valves, pipelines, and heat exchangers, all of different colors, fill the building. "We color coded things to keep it simple." At the heart of the system, two 14-foot-diameter reactors stand 35 feet high. "This thing's like a racehorse."
Such
enthusiasm from Sober comes as no surprise, as several people involved
in the project credit him as a force behind its success. He once ran a
company that built concrete plants and repaired construction equipment,
and he also worked in airfield maintenance. "For 25 years, it's been
mechanical equipment," he remarks. He seized the opportunity to run
the treatment when it came up. "It's fun."
Better Than Expected
How has the treatment plant performed? Owens at EFX reports, "The
performance of the system has been beyond everybody's expectations."
It has achieved over 99.99 percent removal of propylene glycol, resulting
in an average effluent glycol concentration of less than 0.3 milligrams
per liter (equivalent to parts per million). By treating the wastewater
on-site, AIA cut the cost for de-icing fluid collection, containment,
treatment, and disposal by nearly 75 percent in its first season of use.
Beyond that, generating methane gas as a byproduct has resulted in a pleasant surprise. Iachetta says, "The big bang for the buck is that we generate more energy than we use with this system. After heating 30 million gallons of near-freezing stormwater, bringing it up to a temperature of 90 degrees F., and heating two buildings, we still have waste methane we're trying to capture and use for electrical generators." Heating incoming wastewater speeds processing, as bacteria prefer warm food. The system generates biogas equivalent to 46 million BTU per day, the same as 170 million cubic feet of natural gas or 110 gallons of fuel oil per day. Over 14 million BTU per day of this gets burned off as excess.
AIA originally used the anaerobic system to reduce de-icing wastewater to levels local sewage treatment plants could handle without having to charge so much, but they've gone a step further. In warm weather, they discharge effluent by spraying it on the airfields, a technique known as spray irrigation. Besides making the grass grow greener, this acts as a secondary filter. In 2001, they put in an aerobic treatment system, known as a final polishing step, which allows them to discharge directly into Shaker Creek. This uses a 10-foot-diameter, 22-foot-tall cylindrical reactor with a sand bed filter and 95-percent pure oxygen added to the process. The end result: effluent that meets drinking water standards.
With the success of its system, AIA has become well known for its expertise in treating de-icing fluid. Iachetta remarks, "We've done more analysis here at Albany for propylene glycol in the environment than anyone in the world." The airport has four years of data they share with other airports. Representatives from Tokyo and Copenhagen airports as well as large U.S. hubs such as Denver, Dallas, and Nashville have visited the site.
Iachetta has spearheaded efforts to spread the word in his role as environmental compliance officer for the airport and manager and planner of capital projects. He graduated from Cornell University's Master of Regional Planning Program, with emphasis in environmental planning, regulation of toxic substances, and critical area protection law.
In assessing where other airports stand with treating de-icing fluid, Iachetta says, "Many airports are where we were 12 years ago." Some are getting their first enforcement action from environmental agencies. "There is a wide range of unique circumstances and sensitivities at airports across the country," but most are affected by the issue.
Some airports have tried recycling propylene glycol or have made small-scale collection and treatment efforts. Others have established small dedicated deicing pads at the end of a runway or off the apron, but this can result in takeoff delays -- at AIA, airlines de-ice planes at the gate. Some airports have tried treating wastewater in wetlands, but natural biological activity there only works in warm weather. This prompts Iachetta to sum it up: "We have basically designed wetlands in a bottle."
Since getting his Ph.D., Veltman has gone on to become a senior environmental engineer at Olver, Inc., an environmental engineering firm in Blacksburg, Virginia. He gets involved there with anaerobic treatment, in particular with producing ethanol from corn. With a few years lapsed since he carried out his project, he has had a chance to reflect on the AIA system. He designs many water and wastewater treatment plants today, but most are routine and don't involve new or novel applications. "To me, it's exciting to have an opportunity to do something that's a little out of the ordinary. It was very rewarding for me professionally," he relates.
Meanwhile, AIA takes pride knowing they not only solved an immediate pollution problem but can now help airports around the world solve the same problem with a long-term solution that generates more energy than it uses.
Progressive
Engineer
Editor: Tom Gibson
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©2004 Progressive Engineer